This article was automatically translated from the original Turkish version.
The attacks carried out in the United States on September 11, 2001 are regarded as a pivotal turning point in international relations and security policy. In the incident, four passenger aircraft were hijacked by members of Al-Qaeda; two were flown into the North and South Towers of the World Trade Center in New York, one into the Pentagon building in Washington, and the fourth crashed in Pennsylvania after passengers intervened. As a result of these attacks, approximately three thousand people lost their lives, thousands were injured, and extensive destruction occurred in various regions, especially in New York.
The impact of the attacks extended beyond the United States, triggering profound changes in global perceptions of security. The U.S. military interventions in Afghanistan and Iraq under its “War on Terror” policy produced wide-ranging consequences for international law, alliance relations, and regional balances. Moreover, the effects of the attacks on health, the environment, social perceptions, and cultural production have made it necessary to view September 11 as a multidimensional phenomenon.
The aircraft departed at 07:59 and made its last routine radio contact at 08:14. Shortly thereafter, the cockpit was breached. At 08:19, a flight attendant called United Airlines headquarters to report the hijacking; at 08:21, the transponder was turned off, causing secondary radar tracking to be lost. At approximately 08:25, Boston Air Traffic Control confirmed the unusual situation; at 08:38, the Northeast Air Defense Sector (NEADS) was notified.
At 08:46:40, AA 11 struck the North Tower of the World Trade Center; within the same minute, orders were issued for F-15s from Otis Air Base to take off; at 08:53, these aircraft launched but were held in holding patterns due to the lack of a specific target vector. Throughout AA 11’s flight, the transponder being off caused reliance on primary radar returns; communication between air traffic units and airline operations centers was fragmented and disjointed.
The aircraft departed close to its scheduled time, took off at 08:14, and reached cruising altitude at 08:33. Between 08:42 and 08:46, the cockpit was breached; statements regarding knife use and bomb threats were reported by passengers and crew during calls. From 08:47 onward, the transponder code was changed at short intervals; at 08:51, the aircraft deviated from its assigned altitude and did not respond to New York controllers’ calls. At 08:52, a flight attendant informed United’s ground unit that both pilots had been incapacitated and the aircraft was being flown by the hijackers; at the same moment, passenger phone calls reported the situation inside the cabin and that the aircraft was heading toward New York.
At 08:58, the turn was completed and the aircraft entered Manhattan; at 09:03:11, it struck the South Tower. During UA 175’s final approach, rapid changes in altitude and speed were recorded; a wide circular maneuver ensured precise alignment with the target. Despite the fire and smoke affecting visibility around the tower, the flight path remained steady.
AA 77 departed at 08:20 and reached a cruising altitude of approximately 35,000 feet by 08:46. Its last routine radio contact occurred at 08:51; between 08:51 and 08:54, the cockpit was breached; at 08:54, an unauthorized southward turn occurred and the transponder was turned off at 08:56. From this point onward, the aircraft became temporarily undetectable even on primary radar, and different control centers marked it as “lost contact/missing.” At 09:25, the U.S. air traffic system implemented a nationwide ground stop; at 09:32, a rapidly approaching primary target was detected on Dulles radar.
At approximately 09:34, it was determined that the target had changed course over Washington in a wide arc, then descended to low altitude and increased engine power. At 09:37:46, AA 77 struck the Pentagon. The aircraft’s large semicircular maneuver over the capital was designed to adjust its final approach path and to aim at the target at low altitude and high speed. The transponder being off delayed identification and narrowed options for warning and interception.
UA 93 was scheduled to depart at 08:00 but took off at 08:42 due to air traffic congestion. Warnings increased across the sector due to simultaneous events; at 09:24, United Airlines’ ground unit alerted the cockpit of a possible cockpit intrusion. The last routine radio contact occurred at 09:27; the hijacking began at 09:28 and physical intervention occurred in the cabin. At 09:41, the transponder was turned off and the aircraft dropped to primary radar tracking. Passengers and crew communicated the situation via phone calls to the ground; an organized decision to attempt to retake the cockpit began at 09:57.
During this time, irregular fluctuations in altitude and speed were recorded, and sudden movements occurred in the control surfaces. UA 93 crashed at 10:03:11 in a rural area near Shanksville, Pennsylvania. The delayed departure allowed those on board and company units to partially learn about the other attacks; this influenced the timing of the passenger initiative. Post-incident analyses suggested that the intended target of the aircraft may have been one of the symbolic federal buildings in Washington.
American Airlines Flight 11 struck the North Tower at 08:46:40. The impact occurred on the north face of the tower, between approximately the 93rd and 99th floors. The presence of many people in the building who had just begun their morning workday increased the scale of the disaster. The penetration of the fuselage and wings into steel load-bearing columns caused ruptures in the structural framework; the majority of the fuel stored in the wings and fuselage ignited instantly.
The resulting high heat facilitated the ignition of office equipment and interior finishes; fire and smoke moved vertically rapidly through elevator shafts and service cores. In the initial minutes, the nature of the event was not fully understood; however, the speed of flame spread and the geometry of the impact quickly indicated that this was an attack by an aircraft. Immediate fatalities occurred in the impacted floors; escape routes for the floors above were largely blocked.
United Airlines Flight 175 struck the South Tower at 09:03:11. The aircraft approached at a steeper and more inclined angle than the North Tower; the impact occurred between the 77th and 85th floors. Television channels were broadcasting live following the first attack; the second aircraft hitting the tower clearly demonstrated that the event was a coordinated operation. The sudden combustion of fuel created a massive fireball on the exterior; glass and facade elements were scattered outward.
A significant portion of those on the impact floors died immediately from the collision and its aftermath; escape options for the floors above were severely limited. The oblique impact on the South Tower caused asymmetric damage to some load-bearing elements and uneven fire spread across the floor plan. Smoke shifting with the wind affected visibility and breathing differently on various facades.
American Airlines Flight 77 struck the west face of the Pentagon at 09:37:46. The aircraft approached at low altitude and high speed, following a profile very close to ground level and impacting the outer ring. Structural elements at the point of impact suffered severe damage; the ignition of fuel caused fire to spread rapidly, resulting in intense heat accumulation within the first minutes.
The impact created partial collapse and extensive damage in the outer ring of the pentagon-shaped structure. Although the site was documented with fewer camera recordings than New York, physical destruction and debris distribution clearly demonstrated the direct impact of the aircraft. Personnel working in the impacted corridor suffered fatalities; evacuation and firefighting efforts were conducted simultaneously in other sections of the building.
After the hijackings began, the first reflex in the cabin was to use available telephones to inform the outside world. Crew members called airline operations centers, reporting the use of cutting tools, injuries, loss of contact with the cockpit, and passengers being directed to the rear of the aircraft. With the transponders turned off, air traffic control’s technical data diminished; this gap was partially filled by cabin reports. Thus, coordination centers on the ground were able to obtain the first picture of what was happening outside the cockpit on each aircraft through the communications of cabin personnel and passengers.
Communication flow on AA 11 and UA 175 followed similar patterns. On AA 11, flight attendants immediately called the airline’s line after the hijacking began; reports included the use of irritant spray, injuries, and information that certain individuals seated in the front were threatening others. On UA 175, both flight attendants and passengers informed United’s ground unit that the pilots had been incapacitated, the cockpit had been taken over by the hijackers, and the aircraft was performing unusual maneuvers. Some calls mentioned bomb threats, worsening cabin air quality, and passengers gathering toward the rear. These calls indicated that the cockpit door had been forcibly breached and systematic direction was being carried out inside the cabin.
On AA 77, external contact remained limited but decisive. According to several reports from the cabin, cutting tools were used, passengers were forced to the rear, and access to the cockpit was blocked. Immediately after the transponder was turned off, the aircraft’s primary radar trace intermittently disappeared, delaying confirmation processes for both air traffic units and the airline headquarters. Nevertheless, the small number of messages transmitted confirmed that the flight path had been diverted and the cockpit door had been forcibly taken over.
The situation on UA 93 evolved in a different direction. The delayed departure allowed the first news about the other attacks to reach the cabin; passengers and crew learned of the impacts in New York and Washington through conversations with family members and United’s ground unit. This information strengthened the assessment that their situation was part of a coordinated plan targeting symbolic locations. After the hijacking began, details about the number, location, and methods of the hijackers were compiled; a consensus quickly formed on what to do. At 09:57, passengers began a coordinated effort to retake control using available means such as service carts and other cabin equipment.
On cockpit audio recordings, intense movement toward the door, shouting, and sudden control inputs were heard. During this time, it became clear that the hijackers were attempting to shake the aircraft with violent pitching and rolling maneuvers to prevent the cockpit door from being breached. Altitude and speed fluctuated at short intervals, and control inputs became irregular. As the struggle continued, UA 93 crashed at 10:03:11 in a rural area near Shanksville, Pennsylvania. Site findings and analysis of flight and cockpit recordings suggest that the passenger initiative prevented the aircraft from reaching its intended target; the violent maneuvers applied in the final moments may have pushed the aircraft out of control.
A common thread among all four flights was the decisive role of professional reflexes and calm communication by cabin crews. Crew members and passengers transmitted the situation as clearly and concretely as possible through available lines; this allowed ground units to interpret the course of events in an environment where radar and radio data were insufficient. Particularly on UA 93, the effort to gather information and conduct a brief assessment enabled a timely and coordinated resistance.
The two towers of the World Trade Center (WTC 1 and WTC 2) were designed to function on the simple principle of “two rings and connecting bridges.” The outer ring behaved like a continuous shell made of closely spaced steel columns along the facade; it carried most of the wind load. The inner ring formed the “core” containing elevators and stairwells; a significant portion of vertical loads was carried by this core. Floor slabs, extending between the inner core and the outer shell, acted as “bridges” connecting the two rings; thus, the entire system operated as a unified whole.
This design assumed that even if some components were lost, loads could be redistributed through alternative paths. This engineering concept of “redundancy” aimed to ensure that if a single column failed, the load could be transferred to neighboring elements. Additional tie beams at the top of the towers (structural elements at roof level) strengthened the coordinated behavior of the outer shell and the core. Ultimately, the outer shell functioned like a cylinder against wind, the core carried vertical loads, and the floor slabs locked the two systems together.
Flexible interior space usage was intended, with large and easily divisible office areas designed. For this purpose, lightweight steel beams were used in floor slabs; concrete toppings were added to increase rigidity and fire resistance. Vertical circulation was resolved through a “sky lobby” system; express elevators carried passengers from main entrances to intermediate sky lobbies, from which local elevators provided access to individual floors. Each tower contained multiple stairwell shafts within the core; escape continuity was ensured through fire doors and pressurization measures.
Fire safety was addressed through both passive and active measures in accordance with contemporary standards.
Steel load-bearing members were covered with spray-applied fireproofing (a protective layer commonly referred to as “fireproofing spray”) to prolong their resistance under high heat. Automatic sprinklers, detection and alarm systems, and fire hoses were installed throughout the building. This layered approach aimed to protect structural components from heat and support occupant evacuation in the event of a fire.
The possibility of an aircraft impacting the building was evaluated under specific assumptions during the design process. These assessments assumed a collision at low altitude, near landing speed, and with limited fuel load; the anticipated damage was expected to remain localized and firefighting to remain feasible. The goal was to ensure that even if some elements were damaged in the impact zone, the overall structure would remain standing and sufficient time would be provided for evacuation.
Manufacturing and assembly methods were also considered part of the system. Facade panels were produced in workshops and could be rapidly assembled modularly on site. Floor beams and connection elements were standardized. This approach shortened construction time and facilitated replacement of components when maintenance or repair was needed.
When the aircraft struck the towers, the jet fuel stored in the wing tanks and fuselage was instantly dispersed, creating widespread fire fronts on the impact floors and adjacent levels. This initial ignition phase was extremely intense due to the high volatility of the fuel; thereafter, the continuity of the fire was primarily sustained by office furnishings, furniture, carpets, paper, and plastics.
Smoke rapidly rose in areas exposed to high heat, creating a “chimney effect” through elevator shafts and service voids, drawing hot gases upward. Large openings created in the outer shell and broken glass increased oxygen inflow due to wind, altering the direction, speed, and temperature of the fire in some sections.
The mechanical impact of the collision also damaged fire safety layers. Spray-applied fireproofing on steel load-bearing members was dislodged in places due to impact and vibration; thus, exposed steel elements absorbed heat more rapidly. Steel lost a significant portion of its strength and rigidity between approximately 400–600 °C. This loss manifested not as individual columns melting, but as the gradual reduction in capacity of multiple elements over time and the weakening of interdependent load paths.
Floor slabs first expanded under heat, increasing stress at connection points. As heat exposure prolonged, metal fatigue and permanent deformation known as “sagging” became prominent; sagging slabs pulled outer shell columns inward. This inward pull distorted the vertical alignment of some facade columns; from the outside, the columns appeared visibly curved inward. This inward buckling of the tower shell reduced both horizontal rigidity and vertical load-bearing capacity.
The situation in the core region became critically different. Some core columns were severed or severely damaged during impact; the remaining columns bore loads exceeding normal capacity. Fire heat also caused strength loss in core elements; additionally, the surrounding floor slabs, due to sagging, irregularly disrupted the lateral restraint they exerted on the core. This scenario eroded the “cooperative behavior” between the outer shell and the core. Loads could be redistributed temporarily through the designed redundant paths; however, as the fire persisted, this redundancy gradually diminished.
From the perspective of escape and evacuation, parts of the stairwell shafts on the impact floors and above were damaged or filled with smoke. Even in open stairwells, heat and smoke made progress difficult; fire doors, pressurization systems, and alarm mechanisms functioned in some routes but were limited in others due to impact-related damage. Consequently, while evacuation flow continued for a long time in lower floors, conditions on the floors above the impact zone deteriorated rapidly.
An important factor determining fire development was the irregularity in fuel and air supply. Broken facade panels accelerated fire in some floors depending on wind direction, while causing smoke to pool inside other floors. This variability produced situations where one section of a floor heated rapidly enough to collapse, while adjacent sections remained relatively cooler. Thus, damage was patchy rather than uniform; from an engineering perspective, this caused loads to flow in unexpected directions and some connection elements to be overstressed prematurely.
American Airlines Flight 77 struck the west face of the Pentagon at low altitude and high speed. The aircraft, impacting the outer ring of the pentagon-shaped structure, dislodged portions of steel and reinforced concrete load-bearing elements; fires ignited and spread to adjacent rings as the fuselage and fuel advanced inward. The sudden impact created a wide breach line on the facade; immediately afterward, fuel ignition caused rapid temperature increases. The intense heat load and smoke observed in the first minutes resulted in partial collapse in the impact zone.
The Pentagon’s concentric ring structure and corridor voids limited the immediate spread of damage throughout the entire building. Nevertheless, serious ruptures occurred in columns and beams along the impact line; some floor slabs lost their load-bearing capacity. The fire was fueled by office furnishings and interior finishes; however, progress was slowed in areas where sprinklers and fire lines remained functional.
Evacuation and firefighting were conducted simultaneously; personnel working in the impacted corridor suffered fatalities. Site investigations showed that the damage resulted from the combined effect of impact and fire; in sections where structural continuity was preserved, progressive collapse was prevented.
United Airlines Flight 93 crashed in a rural area near Shanksville, Pennsylvania, while passengers and crew were executing a coordinated effort to retake control. After the crash, a deep crater formed on the terrain; debris and personal belongings scattered over a wide area were contained within a security perimeter. Local emergency responders reached the site quickly; the fire was brought under control and civilian harm in the surrounding area was prevented. The rural topography and low population density prevented additional ground casualties.
Site investigations were conducted alongside the recovery and analysis of flight and cockpit voice recorders (black boxes), phone recordings, and radar data. These findings revealed that information was gathered and shared in the cabin after the hijacking; the possibility of targeting symbolic sites in Washington was assessed on board; and a coordinated passenger initiative was organized in response.
It was determined that shortly before the crash, the aircraft performed violent pitching and rolling maneuvers; these were interpreted as attempts to prevent pressure on the cockpit door. Ultimately, the aircraft crashed and disintegrated in an uninhabited area; identification and evidence collection processes at the site were carried out meticulously. Assessments indicated that the passenger and crew initiative may have prevented the aircraft from reaching its intended target.
Immediately after the first impact, New York’s emergency response chain rapidly mobilized; fire, police, and medical teams were dispatched to Lower Manhattan in increasing numbers. The area quickly transformed into a multi-agency intervention zone; vehicle and personnel flow was directed through control points along access routes. FDNY units established temporary command posts at the entrances and ground levels of the towers; interior progress was planned floor by floor via stairwells and service corridors. The widespread failure of elevators slowed vertical access; progress in stairwells affected by impact and fire was partially interrupted.
At the scene, priority was given to ensuring that entering teams did not conflict with evacuation flows. NYPD assumed responsibility for perimeter security and separating pedestrian and vehicle traffic; Port Authority personnel supported interior guidance and public announcement systems to the extent possible. Heat and smoke conditions changed rapidly between floors; even in open stairwells, visibility and breathing were occasionally difficult. Nevertheless, controlled evacuation corridors were established in lower and middle floors; medical triage areas and dispatch points were created in the external environment.
Communication and command-control were among the key challenges on the scene. Multiple units using the same radio frequencies and partial damage to building repeater infrastructure created congestion and dropouts in radio traffic. Consequently, backup methods such as “floor-by-floor reporting” and messenger confirmations were implemented between interior progress teams and external command elements. Teams established rest and regrouping points based on floor heights; oxygen and water resupply and shift changes occurred at these intermediate points.
Firefighting was initially conducted through local fire suppression and monitoring smoke movement. Large openings in the tower facades increased oxygen inflow due to wind, accelerating fire spread in some floors. Progress was slowed in areas where sprinklers and wet lines remained functional; however, as damage to piping and valves increased near the impact zones, water pressure dropped in places. This situation required continuous reassessment of personnel positions and withdrawal thresholds.
The collapse of the South Tower at 09:59 and the North Tower at 10:28 fundamentally changed scene priorities. Numerous personnel and civilians inside the towers were directly affected; the external environment was at risk from dense dust clouds and falling debris. After the collapses, the response shifted from a focus on “interior firefighting” to “debris search and rescue and site security.” Heavy machinery, search dogs, and manual probing methods were used together; incremental progress through the debris was preferred, with attention to new collapse or displacement risks. The heat and smoke of the debris determined the duration and intensity of work periods; teams were rotated on a shift basis.
Logistics and support lines ensured sustainability on the scene. Temporary storage points were established for water, medical supplies, personal protective equipment, and heavy rescue gear; volunteer flow was channeled through registration, direction, and security screening. Nearby hospitals gradually increased capacity; blood donation and psychosocial support lines were activated. Bridges and tunnels were subject to controlled access throughout the critical period; the incident command post was relocated to a larger and safer area over subsequent hours to strengthen interagency coordination.
From a safety perspective, secondary hazards were continuously monitored. Structural instability, suspended heavy elements, hot spots, sharp metal and glass fragments, and air quality necessitated the use of personal protective equipment by teams. Masks and eye protection became standard practice to reduce health effects from dust and smoke. Within this framework, by the end of the first day, a multi-agency, multi-layered crisis management system was established in New York; search and rescue, firefighting, medical logistics, and security functions were restructured to complement each other.
Immediately after the impact, Arlington County Fire Department and neighboring district teams arrived at the scene and quickly established a unified command structure. Priorities were clearly defined; evacuation of personnel inside the building, fire control, and structural stabilization of the impact zone were conducted simultaneously. The concentric ring structure of the pentagon-shaped building and corridor voids prevented heat and smoke load from spreading instantly across the entire mass; however, intense heat, fuel-related fires, and structural damage along the impact line on the west facade complicated the response.
At the scene, security perimeters were established around the impact area due to collapse risks; access was provided only through controlled corridors after risk assessments by structural engineers and search and rescue teams. Foam units and water lines were used together; fuel pools were smothered with foam while internal heat buildup was monitored with thermal cameras. Sprinklers and fire systems functioning in intact areas slowed fire progression; however, pressure losses occurred locally in damaged lines. Evacuation areas were supported by triage stations established near the helipad and parking areas; injured individuals were prioritized for transport to surrounding hospitals.
Command-control and security formed the central axis of the response. Military units worked within a unified command-control structure alongside fire and medical teams; measures for bomb disposal and CBRN (chemical, biological, radiological, nuclear) detection were implemented against the possibility of secondary devices. In the first hours, internal progress was intermittent due to partial collapse and high heat along the impact line; while fire was brought under control, structural stabilization measures such as shoring and damage monitoring were maintained. Field data obtained enabled the incident command to coordinate search and rescue, firefighting, and evidence preservation under a single umbrella in a short time.
Upon United 93’s crash in a rural area, local volunteer fire departments and emergency medical teams reached the site within minutes. The impact created a deep crater in the rural topography and limited-scale fires in the surrounding area; due to low population density, no additional ground casualties occurred. The initial response focused on fire containment, securing the area within a security perimeter, and cutting off civilian access. Within a short time, the incident command was transferred to federal investigative units; the search for flight recorders, grid-based scanning of debris, and evidence preservation procedures were standardized.
Regarding environmental risks, containment barriers and collection trenches were deployed against fuel residues and surface runoff; air and water quality measurements were initiated. The fire was brought under control by initial responders; localized water and foam applications were sufficient. Movement around the site followed a one-way entry-exit principle; the location and assignment of every team entering the site were recorded. Thus, evidence integrity was preserved; at the same time, a smooth information channel was established between local and federal authorities.
In both locations, the common feature of the first hours was the balance between life safety, fire control, and evidence preservation. In the Pentagon, structural safety measures aimed at reducing internal risks; in Shanksville, the planned and layered collection of debris scattered over a wide area stood out. This approach enabled uninterrupted progress in subsequent rescue and recovery efforts as well as official investigations.
In the September 11, 2001 attacks, 2,973 people lost their lives in the United States, excluding the hijackers. New York’s emergency response units suffered losses: 343 members of the New York Fire Department (FDNY), 37 members of the Port Authority Police Department (PAPD), and 23 members of the New York Police Department (NYPD). This toll remains the highest loss of life from a single hostile act on U.S. soil.
Officially, New York authorities recorded 2,749 civilian deaths related to the World Trade Center (WTC) complex; this figure includes building occupants, passengers and crew on the aircraft, and civilians in the surrounding area. The same study estimated the total number of people in the two towers at the moment of impact to be 17,560; of these, 15,410 were evacuated, and WTC “building occupant” deaths were calculated between 2,146 and 2,163. This difference arises from the inclusion of aircraft passengers and crew, first responders, and civilians in the WTC total who were not counted among building occupants.
Evacuation dynamics determined the course of fatalities. According to NIST data, at 08:46, approximately 8,900±750 people were in WTC 1 and 8,540±920 in WTC 2. In WTC 1, 7,470 people (approximately 84%) were rescued, and 1,462–1,533 died. In WTC 2, 7,940 people (approximately 93%) were rescued, and 630–701 died. In both buildings, over 99% of those below the impact floors were evacuated. The 16-minute interval between the two impacts contributed to the survival of approximately 3,000 people in WTC 2 through controlled elevator use and self-initiated evacuations.
Survivors above critical thresholds were limited. In WTC 1, stair and elevator routes above the 91st floor were severed; helicopter evacuation was impossible. In WTC 2, approximately 75% of those above the 78th floor at the moment of impact had descended below the 78th floor; after the impact, at least 18 people above the 78th floor were able to descend using the heavily damaged “Stairwell A” (one of these 18 later died from injuries). A group of 12 firefighters, one PAPD officer, and three civilians survived in “Stairwell B” during the collapse of the North Tower.
At the Pentagon, 125 people died as a result of American Airlines Flight 77’s impact; additionally, all 64 people on the aircraft (including the hijackers) lost their lives. 106 injured individuals were transported to hospitals. In the overall September 11 toll, the 184 people who died at the Pentagon represent the total of “civilian and military personnel including those on the aircraft.”
On United Airlines Flight 93, which crashed in Pennsylvania/Shanksville, there were 44 people: 37 passengers (four of whom were hijackers) and seven crew members. In total, 40 civilians (passengers and crew) lost their lives.
Overall, nearly all those below the impact floors in the WTC were able to evacuate; however, the failure of escape routes and fire/heat conditions in the impact zones and above determined the areas where fatalities were concentrated. The time interval between the impacts allowed tens of thousands in WTC 2 to move and evacuation to accelerate; brief elevator use and self-initiated evacuations increased the number of survivors. However, in the North Tower, no life corridor opened above the 91st floor; in the South Tower, only a small number of people above the 78th floor were able to descend using the single damaged stairwell.
As it became clear within a short time that the attacks were a multi-point, simultaneous operation, federal crisis communication was centralized and operational decisions were implemented in coordination. The White House, in its initial assessments throughout the day, identified the event as a terrorist attack and called on the public to follow official announcements and security unit instructions.
Leaders of defense and homeland security institutions maintained continuous contact with civil aviation and judicial units to sustain information flow; the president’s daily schedule was shaped according to the requirements of this crisis management. The communication line was structured as a unified information stream supporting operations at the scenes in New York, the Pentagon, and Shanksville.
Airspace management became the defining issue of the first hours. The FAA’s Command Center in Herndon implemented the nationwide ground stop order at 09:25; processes leading to complete airspace clearance were initiated simultaneously. Later in the day, civil aviation activity was suspended, and the national airspace remained closed until new security requirements were established.
The Department of Transportation began a phased reopening process for airports that completed security measures on September 13, 2001. During this period, interaction between NORAD and civil aviation units operated under extraordinary pressure; some fighter jets were placed on standby, air patrols were conducted over critical areas, and uncertainties created by multiple hijacking scenarios increased risks of delays and false alarms in civil-military communications.
Official statements during the day emphasized that the investigation would proceed as a terrorist crime and that the sites were secured with evidence integrity maintained. Security levels were raised in the capital and key federal facilities; additional measures were implemented at airports and transportation hubs nationwide. Public information campaigns provided clear and updated guidance on health services, blood donation, volunteer coordination, and supply chains; regular briefings were held to limit the spread of misinformation.
In the evening address to the nation, the scope and nature of the attacks were summarized; the course of the investigation and security priorities were shared with the public. In subsequent days, speeches stated that a long-term and determined struggle would be waged against the threat, not only against the perpetrators but also against structures harboring or supporting them.
By the end of the day, the federal decision chain solidified around the rapid clearance of airspace and its continued closure until new security measures were implemented, uninterrupted communication between defense, civil aviation, and judicial units, and the adoption of a clear, unified public communication strategy by the president and senior officials. This framework was expanded in subsequent days through political and legal steps; operations on the ground, investigations, and public communication became an integrated crisis management system.
In the first weeks after the attacks, the most frequently reported symptom among emergency responders in New York was a new and persistent cough; this condition later became known as “WTC cough.” The syndrome is defined by persistent cough developing after exposure to the site and associated respiratory symptoms requiring at least four weeks of absence from work. In the early phase, this condition was accompanied by obstructive airway disease, airway hyperreactivity, air trapping on imaging, bronchial wall thickening, as well as reflux, chronic rhinosinusitis, and post-traumatic stress symptoms.
The majority of those developing WTC cough belonged to the high-exposure group who were directly exposed to the dust cloud on the morning of September 11 and were on-site within the first 48 hours. These findings were quickly documented thanks to FDNY’s (New York Fire Department) ongoing occupational health monitoring; regular surveys, laboratory tests, spirometry, and lung imaging were initiated for approximately 16,000 rescue and recovery workers. These studies statistically strengthened the link between the conditions emerging after September 11 and exposure.
The dose-response relationship of exposure was reflected in respiratory tests. Measurements conducted in the months following September 11 showed that airway hyperreactivity was particularly pronounced in the high-exposure group who arrived at the site in the morning; according to methacholine provocation tests, this group had a higher likelihood of airway hyperreactivity even six months later, and this condition persisted for up to 12 months. More importantly, FDNY workers showed that airway hyperreactivity could be permanent even 10–12 years later. This persistent airway sensitivity was accompanied clinically by symptoms such as cough, chest tightness, and breathlessness on exertion.
In lung function measurements (spirometry: FEV₁: forced expiratory volume in one second), significant declines were recorded in the first year after September 11: among non-smoking FDNY personnel, firefighters experienced an average decline of −439 mL, and emergency medical services (EMS) personnel experienced −267 mL. No significant recovery was observed over the following 6–7 years; cumulative loss between 2001 and 2008 reached approximately 592 mL for firefighters and 504 mL for EMS workers. Annual loss rates between 2002 and 2008 were approximately 26 mL/year for firefighters and 40 mL/year for EMS workers.
This pattern showed that, unlike the typical recovery within days or weeks after conventional fire-smoke exposure, prolonged functional loss could persist after intense exposure to WTC dust. Additionally, while some workers showed partial recovery over monitoring years, a subgroup experienced accelerated FEV₁ decline that continued for years; this condition was defined as a phenotype called “WTC lung injury (WTC-LI)” characterized by FEV₁ falling below the lower limit of normal.
The nature of exposure and dust composition explained the basis of this lasting effect. WTC dust was a mixture with high alkalinity, dominated by coarse particle fractions and inorganic components, metals, asbestos, hydrocarbons. Coarse particles normally trapped in the upper airways penetrated both upper and lower airways under intense and sudden exposure and increased respiratory effort, resulting in combined manifestations of upper airway (rhinosinusitis, voice hoarseness) and lower airway (obstructive pattern, hyperreactivity) symptoms.
On the scope level, the James Zadroga 9/11 Health and Compensation Act, enacted in 2011, established the World Trade Center Health Program (WTCHP); health monitoring and treatment were consolidated under one umbrella to include rescue efforts beyond FDNY, neighborhood residents, and local workers. Today, tens of thousands of people are monitored and treated under this program due to WTC-related health diagnoses.
Among the first responders and the broad group of volunteers involved in cleanup and debris removal, health problems related to exposure showed a pronounced clustering. Thanks to FDNY’s occupational health monitoring infrastructure established before September 11, regular examinations, laboratory tests, spirometry, and lung imaging were immediately initiated for a cohort of approximately 16,000 individuals; this allowed new diagnoses to be compared with pre-9/11 conditions. The Zadroga Act, enacted in 2011, established the World Trade Center Health Program (WTCHP); in addition to the FDNY program, it included intervention teams outside FDNY, regional residents/workers, and personnel from the Pentagon and Shanksville sites. Today, tens of thousands of people are monitored under this program due to 9/11-related diagnoses.
Occupational illnesses centered on the respiratory and “aerodigestive” systems: chronic rhinosinusitis, gastroesophageal reflux disease (GERD), obstructive and interstitial lung diseases, and sleep apnea were identified from the early years. The syndrome known as “WTC cough” was defined as a condition requiring at least four weeks of absence from work due to persistent cough following exposure; nearly all cases involved individuals who arrived on-site within the first 48 hours and were directly exposed to the dust cloud. This syndrome was observed alongside obstructive airway disease, airway hyperreactivity, air trapping/bronchial wall thickening on CT, GERD, chronic rhinosinusitis, and PTSD.
Airway hyperreactivity and FEV₁ loss were the clearest indicators of the exposure-response relationship. Tests immediately after the event detected obstruction and hyperreactivity; particularly among those on-site that morning, the risk of hyperreactivity according to methacholine provocation tests increased more than sixfold within the first six months. This condition persisted for 12 months and even became permanent in a subgroup after 10–12 years. In the first year, FEV₁ declined by an average of −439 mL for firefighters and −267 mL for EMS personnel; despite pre-9/11 norms, recovery was limited over subsequent years, and a phenotype called “WTC lung injury (WTC-LI)” was defined.
Early clinical studies showed that firefighters with WTC cough exhibited prominent air trapping and bronchial wall thickening on chest CT, with physiological findings consistent with obstruction dominating. The same study reported that the syndrome was observed in approximately 3% of the general workforce and approximately 8% of those on-site at the time of collapse; in most cases, breathlessness, chest discomfort, GERD, and upper airway symptoms accompanied it.
Sleep disorders also became part of the occupational spectrum. Among the 11,701 FDNY workers exposed in the first two weeks after September 11, 44% were found to be at high risk for obstructive sleep apnea (OSA) according to screening scales; among the subgroup undergoing polysomnography, 81% received an OSA diagnosis. As exposure level increased, the likelihood of severe OSA also increased; in the highest exposure group, the odds ratio for severe OSA was calculated at 1.91. It was noted that OSA could occur alongside other WTC-related syndromes such as GERD, chronic rhinosinusitis, and PTSD.
On the inflammatory and systemic disease front, an increase in sarcoidosis was reported; “unusual phenotypes” with cardiac and bone/joint involvement were defined in extrapulmonary manifestations. These findings suggested that inflammation related to WTC was not limited to the lungs. Cancers and cardiovascular outcomes were also part of long-term monitoring. In the period approaching 20 years, the initial lower incidence of lung cancer compared to the general population may have been related to lower smoking rates and the long latent period of solid tumors.
Conversely, it was shown that lung cancer screening in 9/11-exposed groups could be insufficient under classical risk criteria and that model-based screening approaches could capture additional cases. Regarding cardiovascular diseases, myocardial infarction, stroke, and revascularization outcomes were reported more frequently among those with the highest exposure.
Psychiatric effects became an inseparable dimension of the occupational illness spectrum. Post-traumatic stress symptoms, anxiety, and depression were identified among rescue workers and volunteers; these conditions were shown to coexist with respiratory syndromes. Particularly among those diagnosed with WTC cough, concurrent PTSD was reported. This pattern demonstrated that exposure created a professional risk profile encompassing both physical and psychological layers.
The unique nature of exposure—the intense and rapid inhalation of dust with high alkalinity and a coarse particle fraction—affected both upper and lower airways simultaneously. The heavy physical exertion on-site increased respiratory demand; particles normally expected to be trapped in the nasopharynx easily reached distal airways. This physical-chemical reality provided a fundamental framework explaining why workers on-site faced “multiple syndromes.”
The dust-smoke mixture that emerged after the attacks in Lower Manhattan entered homes, schools, and enclosed spaces, showing a density gradient depending on wind direction and distance. Brief “peak” values were even observed during nighttime hours in the early days. This environment heightened sensitivity among children, the elderly, those with respiratory or heart conditions, and pregnant women. The contribution of resuspended dust in indoor environments to total exposure was assessed. During the same period, the dense diesel exhaust from debris removal vehicles further increased the pollutant load; fires at the site continued until December 20, 2001.
In comparative field studies among local residents, 2,166 individuals living within a 1.6 km radius of the World Trade Center were evaluated against a comparison group living farther away. New-onset respiratory symptoms such as cough, wheezing, and breathlessness were more frequently observed among previously healthy nearby residents. These symptoms did not reflect in lung function tests among a small subgroup undergoing spirometry; in other words, a symptom-test discrepancy was observed. Among residents with pre-existing asthma, symptoms worsened and medication use increased. This pattern was consistent with general environmental measurements showing that exposure decreased with distance and time.
Regarding the child population, it was recorded that approximately 3,000 children lived within 1 km of the towers at the time of the attacks and that 5,500 students attended school in the area. The presence of pollutants in indoor environments such as schools and homes created an exposure pattern that could affect children’s lungs and upper airways. In medical and psychosocial monitoring, post-traumatic stress reactions were reported among children in New York; psychological counseling services for Manhattan children were further analyzed. These studies demonstrated the need to monitor not only physical health but also mental health.
Regarding pregnant women, two complementary prospective cohort studies were conducted. In the Mount Sinai cohort (n=187), pregnant women who were inside the towers or within 10 blocks on September 11 were followed; a comparison group of 2,367 women who gave birth in the hospital during the same period without exposure was included. No significant differences were found in average gestational duration or average birth weight; frequencies of preterm birth and low birth weight were not different between groups.
However, the frequency of small-for-gestational-age (SGA) infants (an IUGG indicator) was found to be twice as high among the exposed group (approximately 8.2% versus 3.8%). This increase in SGA persisted even after controlling for maternal age, parity, ethnic origin, infant sex, and smoking history. In the Columbia University sample, birth weight, height, head circumference, and Apgar scores were similar; however, gestational duration was found to be approximately 1.6 days shorter on average among the exposed group. The most likely biological factors contributing to the SGA increase were maternal exposure to fine particulate matter (PM) and polycyclic aromatic hydrocarbons (PAH); no association was found between reported stress levels and SGA.
In the follow-up of these mother-baby cohorts, infants’ growth indicators and early cognitive development were tracked using standardized assessments (e.g., Fagan and Bayley scales). At the end of the first year, mothers were re-interviewed by phone; changes in feeding, breastfeeding, hospitalizations, and environmental factors were recorded. Cognitive assessments were completed for 159 infants at nine months; Bayley tests were administered at one year. Follow-up was planned to continue until at least age three. In this way, the effects of exposure during pregnancy were extended beyond birth to early childhood.
Overall, health effects on the local population exhibited a gradient along the “exposure intensity-distance-time” axis. Community exposures were lower than those of first responders, but new-onset respiratory symptoms increased in nearby areas; individuals with pre-existing respiratory conditions experienced increased visits and medication use. The detection of increased SGA risk among pregnant women confirmed the sensitivity of the mother-fetus unit to environmental pollutants. Therefore, community health monitoring, indoor cleaning, and risk communication were institutionalized as long-term programs; tens of thousands of people were included in the World Trade Center Health Program.
The collapse of the towers produced a unique contaminant mixture in Lower Manhattan. In the inorganic component of settled dust, metals, ionic species, radionuclides, and asbestos; in the organic component, PAHs, PCBs, dioxins and furans, pesticide residues, phthalate esters, brominated diphenyl ethers, and various hydrocarbons were detected. All samples were distinctly alkaline; pH ranged from 9.0 to 11.0. Asbestos content by mass was reported between 0.8–3.0%, lead between 101–625 ppm. Morphologically, fibrous structures (mineral wool, glass fiber, asbestos, wood-paper-cotton fibers) and coarse cement particles dominated.
Size distribution favored the “coarse fraction”: more than 95% of the mass consisted of particles with an aerodynamic diameter greater than 10 µm; the PM2.5 fraction constituted only 0.88–1.98% of the total mass. As particle size decreased, alkalinity decreased, and the smallest fraction approached a more neutral character. In elemental distribution, chlorine was more concentrated in PM2.5 (indicative of high-temperature plastic combustion), Sb/Al/Ti/Mg in the PM10–53 range; Fe/Zn/Ca were concentrated in both PM2.5–10 and PM10–53 fractions. This pattern showed the combined effect of building material-derived coarse particles and combustion-derived fine fractions.
Over time, the environmental pattern followed several phases. In the first days, PM2.5 levels exceeded urban background levels significantly; during calm wind and temperature inversion conditions, peaks occurred at night and decreased on rainy days. As fires subsided, background levels were approached by mid-October; however, demolition and debris removal activities continued to maintain coarse dust in the air until December. The entry of numerous cranes, trucks, and heavy equipment into the site made diesel exhaust an additional pollutant source; the acrid smoke-dust mixture persisted until fires were fully extinguished on December 20, 2001.
Dioxins and similar chlorinated compounds reached unusual levels due to PVC use at the WTC. Measurements near Ground Zero between September 23 and the end of November reported levels of 10–>150 pg TEQ/m³; several blocks away, levels were 1–10 pg TEQ/m³; by December 2001, levels had declined to urban background levels. Initial risk assessments predicted that this increase would not lead to a significant rise in cancer or non-cancer risks; however, the necessity of long-term monitoring was emphasized.
Asbestos became the focus of public concern. Chrysotile asbestos was used as fire insulation up to the 40th floor of the North Tower; hundreds of tons of asbestos were released on September 11. In screening analyses of over 10,000 ambient air samples using TEM/PCM, some early measurements exceeded the TEM clean threshold (70 fibers/mm²); values later fell within EPA standards. No worker exposure exceeding OSHA’s 8-hour TWA standard was detected, but short-term peak exposures in the debris were suggested. Asbestos was detected in settled dust at levels between 0.8–3.0%; indoor dust in nearby apartments occasionally showed higher values than outdoor levels. This situation suggested that cumulative exposure from delayed indoor cleaning in residences could be a significant component.
Regarding metals, intermittent elevations of lead and chlorine as trace elements were observed near the site until mid-October; calcium, however, became prominent especially during October–November. Atmospheric lead levels rose in the first days but did not reach levels creating a persistent high risk. In settled dust, lead content was recorded between 101–625 ppm.
Effects on living areas in Lower Manhattan were multi-layered. The dust-smoke mixture entered homes and schools; particularly, resuspended dust re-aerosolization prolonged indoor exposure. Indoor dust occasionally showed higher asbestos concentrations than outdoor levels. Nearby residents reported increased new-onset respiratory symptoms such as cough, wheezing, and breathlessness; however, spirometry abnormalities were not detected in the small subgroup tested. Residents with pre-existing asthma experienced increased symptoms and medication use. Outdoor EPA cleanup efforts and rainfall gradually reduced the load; however, diesel exhaust from the site and demolition activities negatively affected air quality intermittently until December 2001.
Long-term monitoring was institutionalized. Supported by NIEHS, a multi-institutional research network conducted a comprehensive monitoring program through ambient air measurements, indoor/outdoor settled dust analyses, high-altitude imaging-modeling, experimental inhalation studies, and community/workforce cohorts. Findings clarified the exposure-time-distance gradient and strengthened the link between the “high alkalinity-coarse fraction-combustion-derived fine fraction” triad and health effects.
In summary, the post-attack environmental profile consisted of a mixture of high-alkaline, coarse-grained, building-material-dominated dust gradually declining over time, combined with combustion-derived fine particles and organic contaminants. Despite rapid decline, indoor accumulation and resuspension prolonged exposure in some homes and workplaces.
The perpetrators of the attacks were members of Al-Qaeda operating within a hierarchical structure. The organization’s leader, Osama bin Laden, made the decision for the attacks and outlined the political-strategic framework. In the operational design and execution phase, Khalid Sheikh Mohammed (KSM) led the planning; due to his prior work on projects targeting civil aviation, he transformed the idea of “using aircraft as weapons” into a systematic operational plan.
Among influential figures in the organization’s military wing, Muhammad Atif (Abu Hafs al-Misri) oversaw security and operational preparations; figures such as Mustafa al-Hawsawi and Ali Abdulaziz Ali (Ammar al-Baluchi) managed financial-logistical channels for funding and supply along the Europe and Gulf routes. Ramzi bin al-Shibh served as the communication link between the Hamburg cell and the core in Afghanistan; although unable to join the pilot team due to visa denial, he played a key role in coordinating money transfers, travel, and communications. The Kuala Lumpur meeting in early 2000 and discussions in Afghan camps were turning points in the maturation of the team and assignment of roles.
The execution team consisted of 19 individuals: four pilot-hijackers and fifteen “force elements” designated as supporters. The pilot team comprised Muhammad Atta (AA 11, Egyptian), Marwan al-Shehhi (UA 175, UAE origin), Hani Hanjour (AA 77, Saudi Arabia), and Ziad Jarrah (UA 93, Lebanese). These four individuals joined camps in Afghanistan between 1999 and 2000, directly consulted with leadership regarding the scope and targets of the plan, and were assigned to receive civil aviation training in the United States.
Atta, al-Shehhi, and Jarrah met in Hamburg, Germany, and progressed through the process together; Hani Hanjour was integrated into the plan with his profile of having already begun flight training in the U.S. The “force element” team was primarily selected from Saudi Arabian citizens and entered the U.S. in waves during the spring-summer of 2001; they underwent basic training in close combat and knife use, were trained in rapidly gaining control of passengers and crew in the cabin and forcibly taking over the cockpit, and were familiarized with the site through short domestic trips before being assigned to target flights.
Planning and logistics were conducted with low visibility. Funding and resources totaling several hundred thousand dollars were mobilized through channels extending from Afghanistan-Pakistan to the Gulf; funds were primarily transferred via bank transfers, travel checks, and cash transport methods through the United Arab Emirates to student/personal accounts opened in the U.S.
Hotel, vehicle, flight school, and ticket expenses were covered from these accounts. Excess balances were returned to the Gulf route at the beginning of September. This financial flow was conducted with limited individuals and transactions; money movements were distributed in small amounts and across different city banking operations to avoid attention. Communication favored internet cafes, prepaid phone cards, and brief face-to-face meetings; correspondence used calendar codes and “daily” keywords.
Flight training and operational preparation progressed in two sequential phases. The pilot team registered at various flight schools, primarily in Florida, progressed from single-engine piston aircraft to twin-engine and simulator training, and focused in 2001 on the cockpit layout and cruise-autopilot logic of large passenger aircraft. Hani Hanjour, having attended civilian flight schools in Arizona since the second half of the 1990s, refreshed his familiarity with the 757/767 cockpit layout and flight management systems during the planning period.
The “force element” team was directed toward several days of close combat training, instructions on knife and cutting tool use, techniques for rapidly gaining control of passengers and crew in the cabin, and methods for forcibly taking over the cockpit door. Seat selections prioritized the front rows and areas near the cockpit; groups were distributed across the same flights in five-member or four-member teams.
The visa and travel network was one of the plan’s vulnerable links. A significant portion of the team entered the U.S. on B-1/B-2 tourist/business visas; entries and exits were often conducted via the UAE. The pilot team’s settlement in the U.S. was completed by the mid-2000s; the majority of the “force element” arrived between March and August 2001. Within the country, a “daily life” appearance was maintained through addresses and bank accounts in Florida, New Jersey, Virginia, and Arizona; rental vehicles, short hotel stays, and flight trials were used for final preparations. Atta and al-Shehhi attended simulator and ground classes alternately at flight schools in Florida; Jarrah strengthened his “navigation-radio” practice with additional flight hours; Hanjour focused on large aircraft systems.
Targets and role assignments were finalized no later than the summer of 2001. The two New York targets were selected as flights using 767 aircraft due to flight range-fuel and visual reference advantages. For the Washington target, the cabin layout and schedule of 757 aircraft were considered advantageous; the fourth aircraft’s mission was determined to target another symbolic site in the capital.
Seat plans anticipated gathering near the cockpit shortly after takeoff, two or three individuals gaining control of the rear cabin, and one individual managing the crowd. Cutting tools and sprays were smuggled into the cabin by exploiting gaps in security screening at the time. In the final week, short domestic flights were conducted as “final rehearsals”; teams spent the night of September 10–11 separately in their respective cities.
The composition of identities was predominantly Gulf origin. Fifteen of the nineteen perpetrators were Saudi Arabian citizens; two were from the United Arab Emirates, one from Egypt, and one from Lebanon. The pilot team was selected from profiles with training and relatively long-term international exposure; the “force element” was formed from individuals who could be trained briefly to carry out violence and control duties in the cabin.
Three members of the Hamburg cell (Atta, al-Shehhi, Jarrah) radicalized within European university and work environments; they established direct contact with the organization’s leadership in Afghan camps and were included in the “aircraft plan.” Individuals such as Nawaf al-Hazmi and Khalid al-Mihdhar, who developed early in San Diego and Virginia, carried out preliminary phases of the plan through daily tasks such as establishing residence and obtaining driver’s licenses; they later joined the Washington team.
Secrecy was maintained until the day of the attack. Ticketing was largely completed at the end of August and beginning of September; the rule of boarding multiple flights on the same day was not adopted; each team focused on its own target route. On the morning of the attack, teams traveled separately to the airports, passed through individual security checkpoints, arrived early at the gates, and gathered near the cockpit seats shortly before departure. Shortly after takeoff, forced entry into the cockpit was implemented; methods based on threats and cutting tools were used to break cabin resistance; after the pilots were incapacitated, the aircraft were directed by the hijacker pilots toward their targets.
The organizational traces of the attacks were confirmed in subsequent years through testimonies, documents, and financial movements. Meetings with leadership in Afghanistan, the distribution of funds via the Gulf route, travel cycles along the Hamburg-Karachi-Dubai-U.S. route, flight school registrations and simulator sessions, hotel-vehicle-phone records, and electronic correspondence formed a coherent whole.
A significant portion of the perpetrators lost their lives on the day of the attack; among senior planners, KSM was captured in 2003, individuals such as Ramzi bin al-Shibh and Mustafa al-Hawsawi were arrested, and Osama bin Laden was neutralized in 2011. Thus, the organizational hierarchy of the perpetrators, along with the execution team-planning core-financial-logistical lines, was concretized through both evidence on the ground and subsequent investigation processes.
Immediately after the attacks, the U.S. administration adopted a broad strategic narrative that did not limit the threat to specific organizations but framed it within the “War on Terror.” This approach, reinforced by the 2002 National Security Strategy and subsequent documents, emphasized the principle of “preemptive intervention”; based on the assumption that Cold War deterrence and containment doctrines were inadequate against new threat types, proactive action against states perceived as linked to terrorist organizations was legitimized. During this period, the NATO Council made the decision to invoke Article 5 of the Washington Treaty; under the framework of alliance support, operations such as “Operation Eagle Assist” were implemented. Thus, the U.S. response was structured within a multi-layered framework extending from domestic security to foreign policy and alliance mechanisms.
The most visible transformation in domestic security was the establishment of the Department of Homeland Security (DHS) in 2002 and the reorganization of transportation security. The Aviation and Transportation Security Act, adopted in November 2001, established the Transportation Security Administration (TSA); this was followed in 2002 by the Maritime Transportation Security Act and the Homeland Security Act. The 9/11 Commission report emphasized that following this rapid expansion, resources needed to be allocated based on risk, integrated planning across sectors, and technology investments (e.g., container scanning) needed to be tied to a long-term strategy. In this context, DHS was expected to establish a “prioritization and accountability” regime integrating scattered responsibilities such as critical infrastructure protection, border security, and emergency preparedness.
In the legal framework, Congress’s first response to the attacks was the USA PATRIOT Act. The Commission noted that some controversial provisions of this act were tied to “sunset” clauses, while many other provisions contained updates that adapted to the surveillance conditions of the digital age and facilitated interagency information sharing. The same report emphasized that maintaining the balance between security and freedom required justifying the continuation of extraordinary executive powers with concrete security benefits and appropriate oversight; it also recommended establishing a specific oversight body within the executive to monitor applications. In border security and identification, regulations strengthening entry-exit systems with biometric data and tamper-resistant document standards were institutionalized through the Patriot Act and subsequent laws.
In intelligence restructuring, the 2004 Intelligence Reform and Terrorism Prevention Act constituted a critical turning point. This law established the Director of National Intelligence (DNI) to coordinate 15 agencies under a single umbrella and the National Counterterrorism Center (NCTC) to collect, analyze, and conduct strategic/operational planning of terrorism-related intelligence nationwide. Within this framework, the Privacy and Civil Liberties Oversight Board was envisioned to monitor the impact of measures on civil liberties. These reforms centralized information sharing, budget and personnel transfers, and cooperation between foreign intelligence services under a central planning axis.
In defense, NORAD’s doctrine and mission, previously focused on external aerial threats, were redefined; the Northern Command (USNORTHCOM) was established to be responsible for continental defense. The 9/11 Commission recommended that this transformation be regularly reviewed and that plans’ adequacy and preparedness levels be assessed according to threat scenarios. These military adjustments proceeded parallel to DHS and TSA’s civil security measures in transportation and critical infrastructure.
The implementation’s impact on the ground was evident in the FBI’s transformation toward national security and the strengthening of interagency coordination mechanisms. Joint Terrorism Task Forces (JTTF) expanded their training and standards; the FBI-DHS relationship was institutionalized at the “field level,” primarily in intelligence sharing and coordination with local law enforcement. The NCTC’s strategic-operational planning function created a permanent workflow integrated with DHS’s intelligence/offices and the FBI’s national security structure.
In border security and identification policies, federal standards were advocated for fundamental identification sources such as driver’s licenses and population registries, and the widespread adoption of biometric entry-exit systems. The 9/11 Commission pointed out that the attackers had been able to bypass different processes using forged or incomplete documents; it prioritized developing a risk-based, layered security architecture (in air, sea, and land modes), monitoring high-risk carriers/facilities, and timely sharing of threat intelligence. TSA’s “layered security system” approach was shaped within this framework.
Foreign operations and detention-interrogation practices became one of the most controversial topics globally. Indefinite detentions at Guantanamo Bay and the extraordinary rendition program, along with allegations of secret detention centers and CIA “black sites,” were intensely criticized; the administration acknowledged the existence of certain secret facilities, and international law and human rights debates surrounding these methods intensified. In subsequent years, steps were taken to reframe the interrogation architecture, establish a High-Value Detainee Interrogation Group (HIG) for high-level interrogations, and limit some practices through executive measures.
All these processes initiated a period in which the scale and authority of the U.S. security apparatus rapidly expanded; correspondingly, accountability, protection of freedoms, and legal oversight became central on the agenda. The 9/11 Commission emphasized that the security-freedom balance should not be viewed as a “zero-sum” relationship; it stressed that effective security supports freedoms and freedoms support security. The U.S. response took shape as a multidimensional policy set through institutional restructuring, laws, and regulations domestically; alliances, military doctrine, and operations abroad; and integration of intelligence-law enforcement-transportation-border security in practice.
After September 11, U.S. foreign policy was shaped around the “War on Terror” narrative and the Bush Doctrine, which legitimized preemptive/anticipatory intervention. The doctrine adopted a strategic approach targeting threats linked to weapons of mass destruction and states providing “safe haven” for such threats, challenging the classical understanding of legitimate defense under the United Nations framework.
In his January 29, 2002 speech, the “axis of evil” label was applied to Iraq, Iran, and North Korea as a separate threat category; this framework was decisive in justifying intervention in Iraq. It was noted that this approach, which anticipated the use of force against potential threats, generated strong debates within international law.
In the context of Afghanistan, Security Council Resolutions 1368 and 1373 characterized September 11 as a threat to international peace and security and referenced Article 51 of the UN Charter on individual and collective legitimate defense. However, these resolutions did not explicitly authorize the use of force against Afghanistan. Resolution 1377, dated November 12, 2001, defined terrorism as the principal threat of the century; Resolution 1378, dated November 14, 2001, explicitly condemned the Taliban for providing safe haven to Al-Qaeda.
The U.S. justified its Operation Enduring Freedom, launched on October 7, 2001, on the grounds of legitimate defense and notified the Council in writing on the same day. The legal nature of the intervention was academically debated in terms of the scope of legitimate defense against a non-state actor (Al-Qaeda) and the “indirect responsibility” of the Taliban regime.
NATO announced on September 12 that Article 5 was applicable; with the U.S. evidence deemed sufficient, Article 5 was effectively invoked on October 4, 2001. This was followed by collective measures such as “Eagle Assist,” involving AWACS deployments for U.S. airspace protection, and “Active Endeavour,” controlling Mediterranean maritime traffic. The U.S. utilized bases in Central Asia through a broad coalition search; it provided military support to the Northern Alliance. Contributions from European allies and regional countries enabled rapid progress in aerial operations and special forces-local alliance coordination; the fall of Mazar-i-Sharif on November 9, 2001, broke the Taliban defense.
Political reconstruction was institutionalized through the Bonn process and ISAF. Resolution 1386, adopted by the Council on December 19, 2001, established the International Security Assistance Force (ISAF); its mission was defined as supporting security in Kabul and throughout the country, assisting the transitional government, and contributing to reconstruction and humanitarian activities.
With participation from many countries including Türkiye, ISAF quickly gained full operational capability; in subsequent years, under NATO command, troop levels reached 130,000 personnel. The transition architecture was shaped through the Loya Jirga under President Hamid Karzai; economic revival hopes were brought to the agenda through pipeline and infrastructure projects. However, it was assessed that the large-scale stability mission conducted in a remote geography created new challenges in force generation and civil-military coordination.
The Iraq front was brought to the center of the strategic agenda immediately after Afghanistan. The U.S. administration presented Resolution 1441, adopted on November 8, 2002, as a “final opportunity”; despite Iraq’s 11,807-page declaration denying possession of weapons of mass destruction (WMD), it continued to claim that Iraq was running secret programs. The failure of weapons inspectors to find concrete evidence on the ground and the lack of support in the Council for a new resolution authorizing the use of force led the U.S., the United Kingdom, and a limited number of allies to launch operations on March 20, 2003 without UN authorization.
The justifications for the intervention were the elimination of WMD capacity, severing possible links to terrorism, and overthrowing the authoritarian regime to establish democracy. Baghdad was entered on April 9, 2003; the regime quickly collapsed, with 139 U.S. soldiers lost in the initial phase and civilian casualties estimated in the tens of thousands. WMD were not found in the short term; this deepened debates over the legitimacy of the intervention.
At the policy level, the Iraq intervention was grounded in the Bush Doctrine’s “preventive war” principle. Allegations of Saddam Hussein’s regime having links to Al-Qaeda and possessing WMD were not confirmed by inspection reports or by the majority in the Council. Consequently, international support was much more limited compared to Afghanistan; objections and veto warnings from major actors such as France, Russia, and China gained prominence. Academic and legal assessments emphasized that the Iraq intervention did not meet the conditions of legitimate defense and served as an example of unilateral use of force outside the UN system.
Overall, the Afghanistan intervention was conducted with broad coalition support and institutional reconstruction tools because it targeted a direct terrorist haven linked to September 11 and because NATO’s Article 5 was invoked. The Iraq intervention, however, entered an international legitimacy crisis due to the failure to confirm WMD and terrorism links and the absence of Council authorization.
Both cases transformed U.S. security priorities; they generated new and lasting debates on NATO’s activities outside crisis zones, the testing of UN monitoring mechanisms, and the interpretation of legitimate defense against non-state actors.
After September 11, Türkiye’s security and foreign policy agenda was shaped along two axes. On one hand, solidarity with the U.S. was maintained as a NATO ally; on the other, Türkiye adopted a cautious line to protect its national interests against the U.S.’s new interventionist approach in the Middle East. NATO made the historic decision on September 12, 2001, to invoke Article 5 of the Washington Treaty for the first time; on October 2, when the attacks were accepted as externally sourced, the collective defense clause came into effect, followed by operations such as “Eagle Assist” for U.S. airspace protection and “Active Endeavour” for Mediterranean maritime security. Türkiye acted in harmony with this decision and implementation, contributing to alliance solidarity.
In the context of Afghanistan, Türkiye contributed 1,150 personnel to NATO’s Peace Force (ISAF) and assumed command of this force twice. During this period, Türkiye maintained close coordination with the U.S., the PKK was added to the U.S. list of terrorist organizations, and IMF financial support occurred within this cooperation climate. Thus, Türkiye demonstrated alliance solidarity in combating terrorism both on the ground and institutionally.
The situation in Iraq, however, differed. Ankara consistently emphasized the preservation of Iraq’s territorial integrity, the unacceptable consequences for Türkiye of a potential state formation in the north, and the serious risk of the PKK gaining strength. In intensive negotiations at the beginning of 2003, U.S. requests for freedom of movement on land, air, and sea areas were evaluated; the first memorandum allowing base modernization was accepted on February 6. However, on March 1, 2003, the second memorandum authorizing the deployment of Turkish Armed Forces to Iraq and opening a northern front was not approved by the Turkish Grand National Assembly due to failure to achieve a simple majority.
After the memorandum decision, disappointment arose in the U.S.; the inability to use Turkish territory, including Incirlik, during the initial phase of the operation created operational difficulties for Washington. Türkiye returned to a limited contribution policy on March 20 through a third memorandum allowing airspace use and, if necessary, troop deployment. This process created a trust crisis in Turkish-American relations and temporarily weakened the “strategic partnership” rhetoric.
The occupation of Iraq focused Ankara’s security priorities on risks centered in northern Iraq. The claim that the PKK had approximately 5,000 militants in the region, along with concerns over the status of Kirkuk and the security of Turkmens, became key issues for Türkiye. These concerns were openly expressed by the then Foreign Minister at NATO meetings. Türkiye attempted to manage on-the-ground risks through memoranda extending its authority to combat cross-border terrorism (e.g., 2008). The “sack” incident on July 4, 2003, targeting Turkish Special Forces personnel in Sulaymaniyah, created a new rupture in relations and deepened mutual trust debates.
At the regional level, the U.S.’s interventionist security approach generated new tensions in the Middle East’s political architecture. Under the banner of the “Greater Middle East Project,” democratization, free trade zones, and institutional reform rhetoric were promoted; however, this framework faced criticism as “democracy export from outside.” In energy geopolitics, the region’s weight in global oil and natural gas reserves determined the strategic context of U.S. regional engagement. During this period, talks with Iran followed a trajectory of implicit cooperation in Afghanistan, followed by intensification over the nuclear crisis.
Türkiye’s response to this situation was a multi-layered balancing effort. On one hand, it continued its contribution to Afghanistan under the NATO line and decided to send troops to Lebanon to support crisis management roles; on the other, it preserved territorial integrity, northern state formation risk, and the PKK threat as fundamental parameters in Iraq. After the rejection of the March 1 memorandum, statements from the Turkish Parliament and government emphasized the legitimacy of the decision and the supremacy of parliamentary will. This line created temporary cooling in Turkish-U.S. relations; however, due to Türkiye’s geopolitical position and the nature of bilateral issues surpassing the two countries’ agendas, the strategic importance of relations was preserved in the medium term.
At the social and political level, the Iraqi occupation process and its aftermath reflected in various field studies showing a marked rise in anti-American sentiment in Turkish public opinion. Criticisms of the U.S.’s unilateral policy and the chaos following the occupation created a long-term climate of distrust in Turkish and regional public opinion. This climate led Ankara to maintain a high level of caution in bilateral relations with Washington and to use both hard/ military and soft/institutional tools in addressing security risks in neighboring regions.
Overall, Türkiye sought to balance its obligations within NATO and fragile balances in the Middle East during the post-September 11 period. It maintained a cooperative contribution in Afghanistan; in the Iraq dossier, it adopted a restrictive stance guided by national security priorities such as territorial integrity, the risk of state formation in the north, and the PKK threat. The energy-geopolitical dimension and erosion of regional humanitarian standards strengthened Türkiye’s multilateral diplomacy and selective engagement policy; this framework became the main axis of Türkiye-U.S. relations and Ankara’s regional security approach in subsequent years.
It must be noted that after September 11, 2001, Islamophobia, or more frequently used in literature, Islamophobia, became central to public opinion, media, and political debates. The European Court of Human Rights’ jurisprudence on the balance between hate speech and freedom of expression emphasized the responsibility of politicians to avoid language inciting intolerance, based on context and intent.
The European Commission against Racism and Intolerance (ECRI) within the Council of Europe offered recommendations to include direct calls to hatred based on religion or ethnicity within the scope of criminal offenses. The OSCE’s hate crime guidelines defined such crimes as “bias crimes,” identifying identity-based targeting as the distinguishing element. This framework established fundamental reference points for monitoring threats, attacks, and discrimination against Muslims after September 11.
Immediately after the attacks, Muslims, Arabs, and South Asians in the U.S. faced a sudden increase in hate crimes. Hundreds of incidents were recorded within a short time; mosques and businesses were targeted; two people were killed; public opinion polls indicated a broad segment supporting special identification or stricter security controls for Arabs and Muslims. This climate, combined with government rhetoric and media frameworks, strengthened the “Muslim=terrorist” stereotype.
The expansion of security policies also increased the sense of surveillance in society. The rapid adoption of the Patriot Act expanded surveillance, search-seizure, and indefinite detention powers; the National Security Entry-Exit Registration System (NSEERS) specifically targeted men of Middle Eastern and South Asian origin with fingerprinting and registration obligations. In Los Angeles, plastic handcuffs ran out during fingerprinting applications; nearly a thousand men were detained without knowing what they were accused of; “voluntary interviews” became effectively coercive. These practices triggered fear and withdrawal in Muslim communities; some individuals resorted to personal defense strategies such as leaving the country or changing their names.
Frameworks promoted by political actors, some religious leaders, and media outlets reinforced the identification of Islam with terrorism. “Uncautious, biased rhetoric” in politics and hostile narratives in media mutually reinforced each other; academic observations noted that Islam was placed within narratives of violence and threat for ideological purposes. These narratives created an perception that normalized Islamophobia and provided a basis for legitimizing human rights violations and discriminatory treatment against Muslims.
Across Europe, restrictive practices regarding religious freedom, widespread discrimination, and anti-Islamic rhetoric in mainstream media combined to produce alarming increases in hate crimes after September 11. In Austria, anti-Islamic crimes began to be reported under the far-right monitoring label; in France, 321 racist-foreigner-hating crimes were recorded in 2007 and 467 in 2008, a significant portion targeting Muslims; in Sweden, the number of anti-Islamic crimes increased from 2007 to 2008; similar trends were observed in the United Kingdom. EU Fundamental Rights Agency data showed that “one in three Muslims in Europe had experienced discrimination” and that women and youth were more affected. However, very few European countries systematically monitor and publicly report these attacks.
In daily life, the concrete manifestations of Islamophobia became evident in employment, education, and public visibility. In Europe, job applications were rejected due to headscarves, students were denied entry to classes, and men were dismissed from jobs due to beards. In a French experiment, a résumé with a “Muslim-sounding” name was systematically rejected. Such cases were discussed alongside human rights reports emphasizing that bans on “religious symbols” could violate religious freedom if based on speculation and assumptions.
In the U.S., institutional practices such as “special registration” (NSEERS), fingerprinting, tightened visa procedures, job dismissals, and deportation reinforced the perception that Muslims faced differential treatment in official institutions. Long and intensive searches at airports, removal from flights, and stories related to “SSSS” secondary screenings were widely publicized. Civil society organizations’ annual reports documented that Muslim-targeted harassment, discrimination, and violence complaints increased by approximately one-third between 2004 and 2005 compared to the previous year.
Regarding the diaspora, Turkish-origin communities were also affected by this climate. Literature reports that tens of thousands of Arab and Muslim American citizens were subjected to registration, fingerprinting, and detention procedures; Turks lost their jobs, had their visas denied, and were forced to return to their country; examples were given of individual success and entrepreneurial stories halted due to bureaucratic obstacles. This process strengthened feelings of insecurity, withdrawal, and being profiled within Turkish communities.
However, examples also exist where local-level close contact and coexistence practices partially softened tensions. Particularly in European cities, mosques not only served as places of worship but also hosted iftars and joint events welcoming local officials, facilitating everyday encounters. Such initiatives created “trust-building” spaces that balanced negative stereotypes in media and reduced prejudice.
In conclusion, after September 11, Islamophobia became prominent in both the U.S. and Europe through increased hate crimes, institutional and daily manifestations of discrimination, the impact of security policies on individual freedoms, and the reinforcing role of media and political rhetoric. It was emphasized that monitoring and reporting mechanisms were insufficient, with only a few countries producing regular data.
September 11 was not limited to shaping security and political agendas; it also triggered new forms of expression and debates in the field of culture and art. Across a broad spectrum from theater to cinema, visual arts to popular music, the tone of narratives changed and representational techniques diversified. This change was particularly evident in the prominence of testimony and documentary-based narratives, the questioning of claims of “neutrality,” and the proliferation of anti-Islamic representations.
Documentary theater became a widespread reference point after September 11. The framework drawn by its founding figure, Erwin Piscator, placed historicity and documentary use at the center. When staging a past event, reliance on documents, selection of main characters from real individuals, incorporation of projection, film, and music elements to create informative and interpretive layers, and integration of all these with a specific political perspective were emphasized. This approach reminded that documentary theater was not a “neutral record” but a political representation built on selected documents.
In some plays written after September 11, while addressing terrorism, Afghanistan, or the Iraq war, a discourse claiming “neutrality” emerged, based on the “verbatim” transcription provided by interview techniques. However, this method strengthened the illusion that the text was non-fictional; it obscured the fact that selection, contextualization, and construction were themselves political acts. This contradiction both popularized documentary theater’s tools and sharpened debates about the ideological nature of knowledge produced on stage.
In the United Kingdom and the United States, “verbatim” theater, which rose in the 2000s, popularized methods relying on direct transcription of interviews. Actors, using in-ear devices to listen to real interviews on stage and matching diction, breathing, and emphasis, enhanced the illusion of “direct testimony.” These formal innovations aimed to bring together perpetrator, victim, and witness voices on the same stage to create a pluralistic framework. However, this plurality did not always mean political balance; some productions were criticized for potentially reproducing absolute oppositions between “the West” and “the Islamic world.”
The documentary theater of the post-September 11 period diversified in content and style. Themes such as the transformation of soldiers on the battlefield, Guantanamo detention practices, radicalization, and negotiation with terrorism were addressed on stage with a language blending investigative journalism. The common denominator of plays focusing on these topics (e.g., those discussing military operations, detention regimes, and political violence) was the dramaturgical structuring of documents and testimony. In constructing this framework, it was emphasized that interviews and archival material were not a “neutral mirror” but a selective lens.
In cinema, music, and popular culture, the impact of September 11 spread rapidly through global circulation networks. Hollywood and the American music industry played a decisive role in the global distribution of mass entertainment; through media such as television and the internet, new narratives of security, threat, and identity reached wide audiences. This process brought with it a cultural terrain where social values and daily habits were transformed, local identities eroded, or new tension lines emerged.
In visual arts and media, one of the prominent debates after September 11 was the boundary between freedom of expression and hate speech. Cartoons published in Denmark and certain short films circulating on the internet triggered international tensions due to derogatory representations of Islam and Muslims. Indeed, a 2007 short film and a 2012 production titled “The Innocence of Muslims” triggered widespread protests; attacks on diplomatic missions and loss of life occurred. These examples demonstrated that cultural production could generate political consequences and that debates on artistic expression and social responsibility became sharper after September 11.
From the perspective of collective memory and commemoration, “Ground Zero” became not only a spatial name for destruction but also a permanent space of remembrance and debate. The months-long fires and debris removal activities after the attacks reshaped the physical and symbolic character of the area; together with environmental measurements and monitoring studies, a new “memory geography” was formed in the city’s collective memory. Prolonged air and dust measurements at different points in Lower Manhattan showed that the effects of fires and debris lasted for weeks and months; this continuity reinforced the sense of “post-disaster permanence” in the spatial perception. In this framework, Ground Zero became a memory node where environmental data, urban planning, and commemorative practices intertwined.
The uncertainty immediately following the attacks further weakened the already fragile global economy. Caution in capital movements, withdrawal in consumer behavior, and decline in travel trends were observed. In this context, both demand and employment in service sectors such as tourism, transportation, and accommodation declined. According to World Tourism Organization data, global tourism growth in 2001 approached zero; the shock’s effects simultaneously reflected on capital markets, tourism, and consumer confidence. This wave was felt as simultaneous contraction across international markets and all sub-sectors of the tourism industry.
In financial markets, the first response was suspension of transactions and a shift toward safe assets. Trading in New York’s financial and capital markets was halted; the dollar depreciated against the euro; oil prices rose by $3.6 per barrel in one day to $31.3 per barrel; gold per troy ounce in London rose from $271.40 to $287. European stock markets experienced sharp declines, and some exchanges were temporarily closed. This pattern showed that security risks were being priced and risk aversion was accelerating.
The area most deeply affected by the shock was the aviation sector. The use of passenger aircraft as weapons quickly depressed flight demand, fundamentally affecting airlines’ capacity, personnel, and route planning. According to the International Air Transport Association (IATA), global losses in flights, passengers, and personnel reached one-third.
Revenue fell from $329 billion in 2000 to $307 billion in 2001 and $306 billion in 2002; the sector reported losses of $13 billion in 2001 and $11.3 billion in 2002. Passenger traffic decreased by 2.7% in 2001 and did not return to 2000 levels until 2003. Recovery became evident from 2003 onward; in 2004, revenues rose to $379 billion. These figures showed that the demand shock lasted two years and recovery occurred gradually.
U.S. policy response also rapidly took shape. The Aviation and Transportation Security Act, enacted on September 22, 2001, aimed to reestablish public confidence and sustain the sector. The act provided $3 billion in direct funding for air transportation and allowed up to $10 billion in federal credit support. Additionally, the “September 11 Victims Compensation Fund” was created for those physically harmed and their families. These measures served not only to rebuild the security architecture but also to preserve the financial sustainability of carriers affected by demand and cash flow shocks.
Effects on the tourism industry emerged simultaneously and in a chain reaction. In the first three months after the attacks, there were massive cancellations of group tours and vacation programs; conferences, meetings, and trade fairs were postponed or canceled. Accommodation businesses faced idle capacity; changes in travel psychology strengthened the “wait-and-see” trend. As tourism businesses worldwide faced reservation cancellations, security concerns pulled down both destination preferences and travel frequency. The World Travel and Tourism Council noted that 8.8 million tourism movements were lost across the broad ecosystem including airports, hotels, car rentals, and tour operators. These losses demonstrated the depth and duration of demand contraction.
Regional implications were also evident. Visitor numbers to Mediterranean destinations such as Israel, Egypt, Tunisia, and Morocco declined; Canada’s tourism industry was negatively affected. The interdependent structure of the tourism supply chain (transportation-accommodation-intermediary institutions) caused a break in one link to rapidly spread across the entire sector. During this period, sector managers rapidly updated communication and pricing strategies to restore customer confidence; flexible refund/cancellation terms and security-focused information became prominent.
In Türkiye, the demand outlook already weakened by the February 2001 crisis was reinforced by the post-attack withdrawal in foreign demand. Cancellations increased in flights and hotel reservations; the highest cancellation rate was observed in the German market, with significant cancellations also from Japan, Italy, and the U.S. Airlines and accommodation businesses sought recovery through price discounts and flexible policies. This process led to short-term declines in tourist numbers and tourism revenue; in the medium term, it created a need for intensive marketing and security communication to repair the destination image.
In conclusion, the attacks triggered a simultaneous demand and confidence crisis across a broad spectrum from financial markets to aviation and tourism. U.S.-implemented financial support and security regulations aimed to stabilize aviation; globally, sector revenues gradually recovered between 2003 and 2004. Recovery of tourism losses was possible through improved security perception, flexible commercial practices, and effective communication strategies. In this framework, the economic legacy of September 11 was not limited to short-term fluctuations; it laid the groundwork for lasting restructuring in areas such as security, insurance, cost structure, and demand flexibility.
After September 11, Al-Qaeda shifted from a centralized, camp-based organizational model to a flexible, geographically dispersed “network” model. In this transformation, the 1998 fatwa, which legitimized global violence against the U.S. and its allies, functioned as an ideological framework that expanded the organization’s operational horizon beyond national borders. The fatwa, calling for the killing of “Americans and their allies wherever possible,” promoted a low-cost but high-impact attack style independent of location and time.
Ayman al-Zawahiri’s influence increased in the organization’s ideological and strategic orientation; Zawahiri’s emphasis on “global jihad” pushed Al-Qaeda from a permanent front to a multi-centered structure advancing through cells and local extensions based on targets. During this process, the role-sharing between Osama bin Laden and Zawahiri—one as founding leader, the other as ideological and organizational mind—sustained the organization’s claim to continuity.
In the spread of the Al-Qaeda network, “franchising”-like loose ties were decisive. From the mid-2000s, organizations such as Al-Qaeda in Iraq (AQI), Al-Qaeda in the Arabian Peninsula (AQAP), Al-Qaeda in the Islamic Maghreb (AQIM), Al-Shabaab in East Africa, and Jabhat al-Nusra in Syria operated in different regions, maintaining ideological links to the center while increasing operational autonomy. This diversification enabled the organization to sustain its presence in different areas even during periods of heavy pressure.
In financing and logistics, the organization shifted away from formal banking channels toward easily transportable values such as cash, gold, and diamonds and informal transfer networks. These methods complicated state efforts to cut off terrorist financing; at the same time, they ensured sufficient resource flows for low-cost operations conducted by small cells. Although the U.S. and its partners attempted to target financial networks, the maneuvering space of the leadership and the self-sustaining nature of dispersed local networks limited the effectiveness of these efforts.
Al-Qaeda’s post-September 11 attack pattern, despite failing to carry out another large-scale attack on U.S. soil, gained continuity through bombings and suicide attacks targeting civilian targets in allied countries. In the 2003 Istanbul attacks, synagogues, the British Consulate, and a bank were targeted; the 2004 Madrid train bombings and the 2005 London transit attacks demonstrated the organization’s ability to conduct coordinated, low-perpetrator, high-damage operations in European metropolises. These attacks revealed that Al-Qaeda had become a network capable of achieving results through local contacts and flexible planning rather than remote command.
In the Horn of Africa and East Africa, Al-Qaeda-linked Al-Shabaab’s 2013 raid on the Westgate Shopping Centre in Nairobi served as an example of the organization’s hybrid attack style, targeting urban “soft targets” with prolonged hostage/raid tactics and generating media impact. This style challenged security forces’ preparedness for urban warfare and, combined with selective release or propaganda messaging after the attack, extended the impact of the operation over time.
In terms of leadership, the symbolic weight of bin Laden and Zawahiri, due to the difficulty of capturing or neutralizing them, sustained the network’s morale and mobilization capacity for a long time. The inability to capture leadership suggested that the organization operated with a redundant hierarchy and localized cell architecture: “even if the center weakens, the network survives.” This situation led to the failure of classical “decapitation” strategies to produce expected results quickly.
In the mid-2010s, the rise of ISIS in the Iraq-Syria region created a significant split in the global jihadist ecosystem. ISIS’s media-saturated violence repertoire and claims of territorial control demonstrated its maximum visibility in propaganda-violence components, particularly through images of James Foley’s execution. In contrast, the Al-Qaeda network continued its existence through regional extensions and local partnerships, sustaining a relatively low-visibility but continuous operational and organizational pattern.
By the 2020s, the picture pointed to a terrorism ecosystem where multiple regional networks operated with varying intensities and priorities, rather than a single powerful centralized organization. Structures along the Al-Qaeda line became embedded in local conflict dynamics across a belt stretching from the Arabian Peninsula to the Maghreb and East Africa, updating their funding and human resources through these local channels.
This fragmented structure made it difficult to consume the organization in a single front; conversely, local vulnerabilities sometimes caused capacity fluctuations. As international pressure and cooperation increased after September 11, Al-Qaeda shifted its emphasis from high-profile “external attacks” to sustaining regional networks and building long-term resilience.
In conclusion, since September 11, Al-Qaeda has evolved along the axis of “central core + regional extensions”; it attempted to reduce its vulnerability by dispersing financing, logistics, and propaganda channels. The sharp rise of ISIS further fragmented the global terrorism field; however, the Al-Qaeda network sustained continuity through local partnerships and low-visibility operations. This view created a long-term, multi-spatial security challenge rather than isolated “big attacks.”
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Chronology of the Attacks
Detailed Flight Paths of the Hijacked Aircraft
American Airlines 11 (AA 11) — Boston (Logan) → Los Angeles
United Airlines 175 (UA 175) — Boston (Logan) → Los Angeles
American Airlines 77 (AA 77) — Washington Dulles → Los Angeles
United Airlines 93 (UA 93) — Newark → San Francisco
Impact Moments on the World Trade Center and the Pentagon
North Tower (WTC 1)
South Tower (WTC 2)
Pentagon
Passenger and Crew Responses, the Downfall of United 93
The Twin Towers and the Pentagon: Collapse and Damage Process
Architecture and Structural Resilience Design
Post-Impact Fires and Structural Vulnerabilities
Attack on the Pentagon and Structural Damage
United 93 Crash Site and Consequences
Rescue Operations and Initial Responses
Emergency Response and Scene Organization in New York
Initial Responses at the Pentagon and Shanksville
Pentagon
Shanksville (Pennsylvania)
Deaths and Survivors
Initial Statements by the U.S. President and Government Institutions
Health Effects
WTC Cough and Respiratory Illnesses
Occupational Illnesses Among Rescue Workers and Volunteers
Effects on Children, Pregnant Women, and the Local Population
Environmental Consequences
Perpetrators and Planning Process
U.S. Response and Security Policies
Interventions in Afghanistan and Iraq
Implications for Türkiye and the Middle East
Rise of Islamophobia and Social Implications
Cultural and Artistic Implications
Economic and Tourism Impacts
Al-Qaeda and Transformation in Global Terrorism
