Early on the morning of Tuesday, September 11, 2001, nineteen hijackers took control of four commercial airliners (two Boeing 757s and two Boeing 767s) en route to California after takeoffs from Logan International Airport in Boston, Massachusetts; Newark Liberty International Airport in Newark, New Jersey; and Washington Dulles International Airport in Loudoun and Fairfax counties in Virginia.^[119] Large planes with long flights were selected for hijacking because they would have more fuel.^[120]

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Key info about the four flights
Operator	Flight number	Aircraft type	Time of departure*	Time of crash*	Departed from	En route to	Crash site	Fatalities (There were no survivors from the flights)
Operator	Flight number	Aircraft type	Time of departure*	Time of crash*	Departed from	En route to	Crash site	Crew	Passengers^†	Ground^§	Hijackers	Total^‡
American Airlines	11	Boeing 767-223ER	7:59 a.m.	8:46 a.m.	Logan International Airport	Los Angeles International Airport	North Tower of the World Trade Center, floors 93 to 99	11	76	2,606	5	2,763
United Airlines	175	Boeing 767–222	8:14 a.m.	9:03 am^{[lower-alpha 9]}	Logan International Airport	Los Angeles International Airport	South Tower of the World Trade Center, floors 77 to 85	9	51	2,606	5	2,763
American Airlines	77	Boeing 757–223	8:20 a.m.	9:37 a.m.	Washington Dulles International Airport	Los Angeles International Airport	West wall of Pentagon	6	53	125	5	189
United Airlines	93	Boeing 757–222	8:42 a.m.	10:03 a.m.	Newark Int'l Airport	San Francisco International Airport	Field in Stonycreek Township near Shanksville	7	33	0	4	44
Totals								33	213	2,731	19	2,996

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* Eastern Daylight Time (UTC−04:00)
^† Excluding hijackers
^§ Including emergency workers
^‡ Including hijackers

The four crashes

The North Tower shortly after the American Airlines Flight 11 crash, the first such attack

United Airlines Flight 175 crashes into 2 World Trade Center. The second attack.

Security camera footage of American Airlines Flight 77 crashing into the Pentagon;^[121] the plane collides with the Pentagon approximately 86 seconds after the start of the recording. The third attack.

The crash site of the fourth hijacked plane, United Airlines Flight 93, near Stonycreek Township

At 7:59 am, American Airlines Flight 11 took off from Logan International Airport in Boston.^[122] Fifteen minutes into the flight, five hijackers armed with boxcutters took over the plane, injuring at least three people (and possibly killing one)^[123]^[124]^[125] before forcing their way into the cockpit. The terrorists also displayed an apparent explosive and sprayed mace into the cabin, to frighten the hostages into submission and further hinder resistance.^[126] Back at Logan, United Airlines Flight 175 took off at 8:14 am, approximately the same time as Flight 11's hijacking.^[127] Hundreds of miles southwest at Dulles International Airport, American Airlines Flight 77 left the runway at 8:20 am.^[127] Flight 175's journey proceeded normally for 28 minutes until 8:42 am, when a group of five hijacked the plane, murdering both pilots and stabbing several crew members before assuming control of the aircraft. These hijackers also used bomb threats to instil fear into the passengers and crew,^[128] also spraying chemical weapons to disable any opposition.^[129] Concurrently, United Airlines Flight 93 departed from Newark International Airport in New Jersey;^[127] originally scheduled to pull away from the gate at 8:00 am, the plane was running 42 minutes late.

At 8:46 am, Flight 11 was deliberately crashed into the north face of the World Trade Center's North Tower (1 WTC) between the 93rd and 99th floors,^[130] although the initial presumption by many was that it was an accident.^[131] At 8:51 am, American Airlines Flight 77 was also taken over by another group of five who forcibly entered the cockpit 31 minutes after takeoff.^[132] Although the hijackers on this flight were equipped with knives,^[133] there were no reports of anyone on board being stabbed, nor did the two people who made phone calls mention the use of mace or a bomb threat.

Seventeen minutes after the first plane crashed into the North Tower, Flight 175 was flown into the South Tower's southern facade (2 WTC) between the 77th and 85th floors^[134] at 9:03 am,^{[lower-alpha 9]} demonstrating that the first crash was not an accident, but rather a deliberate act of terrorism.^[135]^[136]

Four men aboard Flight 93 struck suddenly, killing at least one passenger, after having waited 46 minutes to make their move—a holdup that proved disastrous for the terrorists when combined with the delayed takeoff from the runway;^[137] they stormed the cockpit and seized control of the plane at 9:28 am, turning the plane eastbound and setting course for Washington, D.C.^[138] Much like their counterparts on the first two flights, the fourth team also used bomb threats and filled the cabin with mace.^[139]

Nine minutes after Flight 93's hijacking, Flight 77 crashed into the west side of the Pentagon.^[140] Because of the two delays,^[141] the passengers and crew of Flight 93 had time to be made aware of the previous attacks through phone calls to the ground, and as a result an uprising was hastily organized to take control of the aircraft at 9:57 am.^[142] Within minutes, passengers had fought their way to the front of the cabin and began breaking down the cockpit door. Fearing their captives would gain the upper hand, the hijackers rolled the plane and pitched it into a nosedive,^[143]^[144] crashing into a field near Shanksville, Pennsylvania, southeast of Pittsburgh, at 10:03 am. The plane was about twenty minutes away from reaching D.C. at the time of the crash, and its target is believed to have been either the Capitol Building or the White House.^[120]^[142]

Some passengers and crew members who called from the aircraft using the cabin air phone service and mobile phones provided details: several hijackers were aboard each plane; they used mace, tear gas, or pepper spray to overcome attendants; and some people aboard had been stabbed.^[145] Reports indicated hijackers stabbed and killed pilots, flight attendants, and one or more passengers.^[119]^[146] According to the 9/11 Commission's final report, the hijackers had recently purchased multi-function hand tools and assorted Leatherman-type utility knives with locking blades (which were not forbidden to passengers at the time), but these were not found among the possessions left behind by the hijackers.^[147]^[148] A flight attendant on Flight 11, a passenger on Flight 175, and passengers on Flight 93 said the hijackers had bombs, but one of the passengers said he thought the bombs were fake. The FBI found no traces of explosives at the crash sites, and the 9/11 Commission concluded that the bombs were probably fake.^[119] On at least two of the hijacked flights—American 11 and United 93—the terrorists claimed over the PA system that they were taking hostages and were returning to the airport to have a ransom demand met, a clear attempt to prevent passengers from fighting back. Both attempts failed, however, as both hijacker pilots in these instances (Mohamed Atta^[149] and Ziad Jarrah,^[150] respectively) keyed the wrong switch and mistakenly transmitted their messages to ATC instead of the people on the plane as intended, tipping off the flight controllers that the planes had been hijacked.

Three buildings in the World Trade Center collapsed due to fire-induced structural failure. Although the South Tower was struck 17 minutes after the North Tower, the plane's impact zone was far lower, at a much faster speed, and into a corner, with the unevenly-balanced additional structural weight causing it to collapse first at 9:59 am,^[151]^: 80^[152]^: 322 having burned for 56 minutes^{[lower-alpha 11]} in the fire caused by the crash of United Airlines Flight 175 and the explosion of its fuel. The North Tower lasted another 29 minutes before collapsing at 10:28 am,^{[lower-alpha 12]} one hour and forty-two minutes^{[lower-alpha 10]} after being struck by American Airlines Flight 11. When the North Tower collapsed, debris fell on the nearby 7 World Trade Center building (7 WTC), damaging the building and starting fires. These fires burned for nearly seven hours, compromising the building's structural integrity, and 7 WTC collapsed at 5:21 pm.^[156]^[157] The west side of the Pentagon sustained significant damage.

At 9:42 am, the Federal Aviation Administration (FAA) grounded all civilian aircraft within the continental U.S., and civilian aircraft already in flight were told to land immediately.^[158] All international civilian aircraft were either turned back or redirected to airports in Canada or Mexico, and were banned from landing on United States territory for three days.^[159] The attacks created widespread confusion among news organizations and air traffic controllers. Among unconfirmed and often contradictory news reports aired throughout the day, one of the most prevalent claimed a car bomb had been detonated at the U.S. State Department's headquarters in Washington, D.C.^[160] Another jet (Delta Air Lines Flight 1989) was suspected of having been hijacked, but the aircraft responded to controllers and landed safely in Cleveland, Ohio.^[161]

In an April 2002 interview, Khalid Sheikh Mohammed and Ramzi bin al-Shibh, who are believed to have organized the attacks, said Flight 93's intended target was the United States Capitol, not the White House.^[162] During the planning stage of the attacks, Mohamed Atta (Flight 11's hijacker and pilot) thought the White House might be too tough a target and sought an assessment from Hani Hanjour (who hijacked and piloted Flight 77).^[163] Mohammed said Al-Qaeda initially planned to target nuclear installations rather than the World Trade Center and the Pentagon, but decided against it, fearing things could "get out of control".^[164] Final decisions on targets, according to Mohammed, were left in the hands of the pilots.^[163] If any pilot could not reach his intended target, he was to crash the plane.^[120]

Casualties

The attack on the World Trade Center's North Tower single-handedly^{[lower-alpha 13]} made 9/11 the deadliest act of terrorism in world history.^[167] Taken together, the four crashes caused the deaths of 2,996 people (including the hijackers) and injured thousands more.^[168] The death toll included 265 on the four planes (from which there were no survivors); 2,606 in the World Trade Center and in the surrounding area; and 125 at the Pentagon.^[169]^[170] Most who died were civilians, as well as 343 firefighters, 72 law enforcement officers, 55 military personnel, and the 19 terrorists.^[171]^[172] After New York, New Jersey lost the most state citizens.^[173] More than 90 countries lost citizens in the attacks.^[174]

In New York City, more than 90% of the workers and visitors who died in the towers had been at or above the points of impact. In the North Tower, between 1,344^[175] and 1,402^[176] people were at, above or one floor below the point of impact and all died. Hundreds were killed instantly the moment the plane struck.^[177] The estimated 800 people^[178] who survived the impact were trapped and died in the fires or from smoke inhalation; fell or jumped from the tower to escape the smoke and flames; or were killed in the building's collapse. The destruction of all three staircases in the North Tower when Flight 11 hit made it impossible for anyone from the impact zone upward to escape. 107 people not trapped by the impact died.^[179] When Flight 11 struck between floors 93 and 99, the 92nd floor was also rendered inescapable when its crash severed all elevator shafts while debris falling from its impact zone blocked the stairwells, ensuring the deaths of all 69 workers on the floor immediately below the point of impact.

In the South Tower, around 600 people were on or above the 77th floor when Flight 175 struck and few survived. As with the North Tower, hundreds were killed at the moment of impact. Unlike those in the North Tower, the estimated 300 survivors^[178] of the crash were not technically trapped by the damage done by Flight 175's impact, but most were either unaware that a means of escape still existed or were unable to use it. One stairway, Stairwell A, narrowly avoided being destroyed as Flight 175 crashed through the building, allowing 14 people located on the floors of impact (including Stanley Praimnath, a man who saw the plane coming at him) and four more from the floors above to escape. New York City 9-1-1 operators who received calls from people inside the tower were not well informed of the situation as it rapidly unfolded and as a result, told callers not to descend the tower on their own.^[180] In total, 630 people died in the South Tower, fewer than half the number killed in the North Tower.^[179] Of the 100–200 people witnessed jumping or falling to their deaths that morning,^[181] only three recorded sightings were from the South Tower.^[182]^: 86 Casualties in the South Tower were significantly reduced because some occupants decided to leave the building immediately following the first crash, and because Eric Eisenberg, an executive at AON Insurance, made the decision to evacuate the floors occupied by AON (floors 92 and 98–105) in the moments following the impact of Flight 11. The 17-minute gap allowed over 900 of the 1,100 AON employees present on-site to evacuate from above the 77th floor before the South Tower was struck; Eisenberg was among the nearly 200 who did not escape. Similar pre-impact evacuations were carried out by companies such as Fiduciary Trust, CSC, and Euro Brokers, all of whom had offices on floors above the point of impact. The failure to order a full evacuation of the South Tower after the first plane crash into the North Tower was described by USA Today as "one of the day's great tragedies".^[183]

As exemplified in the photograph The Falling Man, more than 200 people fell to their deaths from the burning towers, most of whom were forced to jump to escape the extreme heat, fire and smoke.^[184] Some occupants of each tower above the point of impact made their way toward the roof in the hope of helicopter rescue, but the roof access doors were locked.^[185] No plan existed for helicopter rescues, and the combination of roof equipment, thick smoke and intense heat prevented helicopters from approaching.^[186]

At the World Trade Center complex, a total of 414 emergency workers died as they tried to rescue people and fight fires, while another law enforcement officer was separately killed when United 93 crashed. The New York City Fire Department (FDNY) lost 343 firefighters, including a chaplain and two paramedics.^[187]^[188]^[189] The New York City Police Department (NYPD) lost 23 officers.^[190] The Port Authority Police Department (PAPD) lost 37 officers.^[191] Eight emergency medical technicians (EMTs) and paramedics from private emergency medical services (EMS) units were killed.^[192] Almost all of the emergency personnel who died at the scene that day were killed as a result of the towers collapsing, with the exception of one who was struck by a civilian falling from the upper floors of the South Tower.^[193]

Cantor Fitzgerald L.P. (an investment bank on the North Tower's 101st–105th floors) lost 658 employees, considerably more than any other employer.^[194] Marsh Inc., located immediately below Cantor Fitzgerald on floors 93–100, lost 358 employees,^[195]^[196] and 175 employees of Aon Corporation were also killed.^[197] The National Institute of Standards and Technology (NIST) estimated that about 17,400 civilians were in the World Trade Center complex at the time of the attacks.^[198]^: xxxiii Turnstile counts from the Port Authority suggest 14,154 people were typically in the Twin Towers by 8:45 a.m.^[199] Most people below the impact zone safely evacuated the buildings.^[200]

In Arlington County, Virginia, 125 Pentagon workers died when Flight 77 crashed into the building's western side. 70 were civilians and 55 were military personnel, many of whom worked for the United States Army or the United States Navy. The Army lost 47 civilian employees; six civilian contractors; and 22 soldiers, while the Navy lost six civilian employees; three civilian contractors; and 33 sailors. Seven Defense Intelligence Agency (DIA) civilian employees died, and one Office of the Secretary of Defense (OSD) contractor.^[201]^[202]^[203] Lieutenant General Timothy Maude, an Army Deputy Chief of Staff, was the highest-ranking military official killed at the Pentagon.^[204]

Weeks after the attack, the death toll was estimated to be over 6,000, more than twice the number of deaths eventually confirmed.^[205] The city was only able to identify remains for about 1,600 of the World Trade Center victims. The medical examiner's office collected "about 10,000 unidentified bone and tissue fragments that cannot be matched to the list of the dead".^[206] Bone fragments were still being found in 2006 by workers who were preparing to demolish the damaged Deutsche Bank Building.^[207]

In 2010, a team of anthropologists and archaeologists searched for human remains and personal items at the Fresh Kills Landfill, where 72 more human remains were recovered, bringing the total found to 1,845. DNA profiling continues in an attempt to identify additional victims.^[208]^[209]^[210] In 2014, three coffin-size cases carrying 7,930 unidentified remains were transferred to a medical examiner's repository located at the same site as the National September 11 Memorial & Museum, but separated from the site by a wall.^[211] Victims' families are permitted to visit a private "reflection room" which is closed to the public. The choice to place the remains in an underground area attached to a museum has been controversial; families of some victims have attempted to have the remains instead interred in a separate, above-ground monument.^[212]

In July 2011, a team of scientists at the Office of Chief Medical Examiner continued efforts to identify remains, in the hope that improved technology will allow them to identify other victims.^[210] In August 2017, the 1,641st victim was identified as a result of newly available DNA technology,^[213] and a 1,642nd during July 2018.^[214] Three more victims were identified in October 2019,^[215] two in September 2021^[216] and an additional two in September 2023.^[217] As of September 2023, 1,104 victims remain unidentified,^[217] amounting to 40% of the deaths in the World Trade Center attacks.^[216] On September 25, 2023, the FDNY reported that with the death of EMT Hilda Vannata and retired firefighter Robert Fulco, marking the 342nd and 343rd deaths from 9/11-related illnesses, the department had now lost the same number of firefighters, EMTs, and civilian members to 9/11-related illnesses as it did on the day of the attacks.^[218]^[219]

Damage

Along with the 110-floor Twin Towers, numerous other buildings at the World Trade Center site were destroyed or badly damaged, including WTC buildings 3 through 7 and St. Nicholas Greek Orthodox Church.^[220] The North Tower, South Tower, the Marriott Hotel (3 WTC), and 7 WTC were destroyed. The U.S. Customs House (6 World Trade Center), 4 World Trade Center, 5 World Trade Center, and both pedestrian bridges connecting buildings were severely damaged. All surrounding streets, including Church, Fulton, and Greenwich Streets, plus NY 9A (the West Side Highway), were in ruins.^[221] The Deutsche Bank Building (still popularly referred to as the Bankers Trust Building) on 130 Liberty Street was partially damaged and demolished some years later, starting in 2007.^[222]^[223] Buildings of the World Financial Center also suffered damage.^[222] The last fires at the World Trade Center site were extinguished on December 20, exactly 100 days after the attacks.^[224]

The Deutsche Bank Building across Liberty Street from the World Trade Center complex was later condemned as uninhabitable because of toxic conditions inside the office tower and was deconstructed.^[225]^[226] The Borough of Manhattan Community College's Fiterman Hall at 30 West Broadway was condemned due to extensive damage from the attacks, and then reopened in 2012.^[227]

Other neighbouring buildings (including 90 West Street and the Verizon Building) suffered major damage but have been restored.^[228] World Financial Center buildings, One Liberty Plaza, the Millenium Hilton, and 90 Church Street had moderate damage and have since been restored.^[229] Communications equipment on top of the North Tower was also destroyed, with only WCBS-TV maintaining a backup transmitter on the Empire State Building, but media stations were quickly able to reroute the signals and resume their broadcasts.^[220]^[230]

The PATH train system's World Trade Center station was located under the complex. As a result, the station was demolished when the towers collapsed, and the tunnels leading to Exchange Place station in Jersey City, New Jersey, were flooded with water.^[231] The station was rebuilt as the $4 billion World Trade Center Transportation Hub, which reopened in March 2015.^[232]^[233] The Cortlandt Street station on the New York City Subway's IRT Broadway–Seventh Avenue Line was also in close proximity to the World Trade Center complex, and the entire station, along with the surrounding track, was reduced to rubble.^[234] The latter station was rebuilt and reopened to the public on September 8, 2018.^[235] The Pentagon was extensively damaged by the impact of American Airlines Flight 77 and the ensuing fires, causing one section of the building to collapse.^[236] As the plane approached the Pentagon, its wings knocked down light poles and its right engine hit a power generator before crashing into the western side of the building.^[237]^[238] The plane hit the Pentagon at the first-floor level. The front part of the fuselage disintegrated on impact, while the mid and tail sections kept moving for another fraction of a second.^[239] Debris from the tail section penetrated the furthest into the building, breaking through 310 feet (94 m) of the three outermost of the building's five rings.^[239]^[240]

Rescue efforts

The New York City Fire Department (FDNY) deployed more than 200 units (approximately half of the department) to the World Trade Center.^[241] Their efforts were supplemented by numerous off-duty firefighters and emergency medical technicians.^[242]^[241]^[243] The New York City Police Department (NYPD) sent its Emergency Service Units and other police personnel and deployed its aviation unit.^[244] The NYPD aviation unit assessed the situation and decided that helicopter rescues from the towers were not feasible.^[245] Numerous police officers of the Port Authority Police Department (PAPD) also participated in rescue efforts.^[246] Once on the scene, the FDNY, the NYPD, and the PAPD did not coordinate efforts and performed redundant searches for civilians.^[242]^[247]

As conditions deteriorated, the NYPD aviation unit relayed information to police commanders, who issued orders for personnel to evacuate the towers; most NYPD officers were able to safely evacuate before the buildings collapsed.^[247]^[248] With separate command posts set up and incompatible radio communications between the agencies, warnings were not passed along to FDNY commanders.^[249]

After the first tower collapsed, FDNY commanders issued evacuation warnings. Due to technical difficulties with malfunctioning radio repeater systems, many firefighters never heard the evacuation orders. 9-1-1 dispatchers also received information from callers that was not passed along to commanders on the scene.^[241]