The September 11 attacks (often referred to as September 11th or 9/11) were a series of coordinated suicide attacks by al-Qaeda upon the United States on September 11, 2001. On that morning, 19 al-Qaeda terrorists hijacked four commercial passenger jet airliners. The hijackers intentionally crashed two of the airliners into the Twin Towers of the World Trade Center in New York City, killing everyone on board and many others working in the buildings.

Both buildings collapsed within two hours, destroying nearby buildings and damaging others. The hijackers crashed a third airliner into the Pentagon in Arlington, Virginia, just outside Washington, D.C. The fourth plane crashed into a field near Shanksville in rural Pennsylvania after some of its passengers and flight crew attempted to retake control of the plane, which the hijackers had redirected toward Washington, D.C. There were no survivors from any of the flights.

The death toll of the attacks was 2,996, including the 19 hijackers. The overwhelming majority of casualties were civilians, including nationals of over 70 countries. In addition, there was at least one secondary death – one person was ruled by a medical examiner to have died from lung disease due to exposure to dust from the World Trade Center’s collapse.

The United States responded to the attacks by launching the War on Terror: it invaded Afghanistan to depose the Taliban, who had harbored al-Qaeda terrorists. The United States also enacted the USA PATRIOT Act. Many other countries also strengthened their anti-terrorism legislation and expanded law enforcement powers. Some American stock exchanges stayed closed for the rest of the week following the attack and posted enormous losses upon reopening, especially in the airline and insurance industries. The destruction of billions of dollars’ worth of office space caused serious damage to the economy of Lower Manhattan.

The damage to the Pentagon was cleared and repaired within a year, and the Pentagon Memorial was built adjacent to the building. The rebuilding process has started on the World Trade Center site. In 2006, a new office tower was completed on the site of 7 World Trade Center. The new 1 World Trade Center is currently under construction at the site and, at 1,776 ft (541 m) upon completion in 2013, it will become one of the tallest buildings in North America. Three more towers were originally expected to be built between 2007 and 2012 on the site. Ground was broken for the Flight 93 National Memorial on November 8, 2009, and the first phase of construction is expected to be ready for the 10th anniversary of the attacks on September 11, 2011.

Attacks

Early on the morning of September 11, 2001, nineteen hijackers took control of four commercial airliners en route to San Francisco and Los Angeles from Boston, Newark, and Washington, D.C. (Washington Dulles International Airport). At 8:46 a.m., American Airlines Flight 11 was crashed into the World Trade Center’s North Tower, followed by United Airlines Flight 175 which hit the South Tower at 9:03 a.m.

Another group of hijackers flew American Airlines Flight 77 into the Pentagon at 9:37 a.m. A fourth flight, United Airlines Flight 93 crashed near Shanksville, Pennsylvania at 10:03 a.m, after the passengers on board engaged in a fight with the hijackers. Its ultimate target was thought to be either the Capitol (the meeting place of the United States Congress) or the White House.

In a September 2002 interview conducted by documentary-maker Yosri Fouda, an al Jazeera journalist, Khalid Sheikh Mohammed and Ramzi Binalshibh stated that the fourth hijacked plane was heading for the United States Capitol, not for the White House.

They further stated that al-Qaeda initially planned to fly hijacked jets into nuclear installations rather than the World Trade Center and the Pentagon, but it was decided not to attack nuclear power plants “for the moment” because of fears it could “get out of control”.

During the hijacking of the airplanes, the hijackers used weapons to stab and kill aircraft pilots, flight attendants and passengers. Reports from phone callers from the planes indicated that knives were used by the hijackers to stab attendants and in at least one case, a passenger, during two of the hijackings.

Some passengers were able to make phone calls using the cabin airphone service and mobile phones, and provide details, including that several hijackers were aboard each plane, that mace or other form of noxious chemical spray, such as tear gas or pepper spray was used, and that some people aboard had been stabbed.

The 9/11 Commission established that two of the hijackers had recently purchased Leatherman multi-function hand tools. A flight attendant on Flight 11, a passenger on Flight 175, and passengers on Flight 93 mentioned that the hijackers had bombs, but one of the passengers also mentioned he thought the bombs were fake. No traces of explosives were found at the crash sites, and the 9/11 Commission believed the bombs were probably fake.

On United Airlines Flight 93, black box recordings revealed that crew and passengers attempted to seize control of the plane from the hijackers after learning through phone calls that similarly hijacked planes had been crashed into buildings that morning.

According to the transcript of Flight 93’s recorder, one of the hijackers gave the order to roll the plane once it became evident that they would lose control of the plane to the passengers. Soon afterward, the aircraft crashed into a field near Shanksville in Stonycreek Township, Somerset County, Pennsylvania, at 10:03:11 a.m.

local time (14:03:11 UTC). Khalid Sheikh Mohammed, organizer of the attacks, mentioned in a 2002 interview with Yosri Fouda that Flight 93’s target was the United States Capitol, which was given the code name “the Faculty of Law”.

Three buildings in the World Trade Center Complex collapsed due to structural failure on the day of the attack. The south tower (2 WTC) fell at approximately 9:59 a.m., after burning for 56 minutes in a fire caused by the impact of United Airlines Flight 175. The north tower (1 WTC) collapsed at 10:28 a.m., after burning for approximately 102 minutes. When the north tower collapsed, debris that fell on the nearby 7 World Trade Center (7 WTC) building damaged it and initiated fires. These fires burned for hours and compromised the building’s structural integrity, which led to the crumbling of the east penthouse at 5:20 p.m. and to the complete collapse of the building at 5:21 p.m.

The attacks created widespread confusion among news organizations and air traffic controllers across the United States. All international civilian air traffic was banned from landing on U.S. soil for three days. Aircraft already in flight were either turned back or redirected to airports in Canada or Mexico. News sources aired unconfirmed and often contradictory reports throughout the day.

One of the most prevalent of these reported that a car bomb had been detonated at the U.S. State Department’s headquarters in Washington, D.C. Soon after reporting for the first time on the Pentagon crash, some news media also briefly reported that a fire had broken out on the National Mall. Another report went out on the Associated Press wire, claiming that a Delta Air Lines airliner—Flight 1989—had been hijacked. This report, too, turned out to be in error; the plane was briefly thought to represent a hijack risk, but it responded to controllers and landed safely in Cleveland, Ohio.

Casualties

There were a total of 2,996 deaths, including the 19 hijackers and 2,977 victims. The victims were distributed as follows: 246 on the four planes (from which there were no survivors), 2,606 in New York City in the towers and on the ground, and 125 at the Pentagon. All the deaths in the attacks were civilians except for 55 military personnel killed at the Pentagon.

More than 90 countries lost citizens in the attacks on the World Trade Center. In 2007, the New York City medical examiner’s office added Felicia Dunn-Jones to the official death toll from the September 11 attacks. Dunn-Jones died five months after 9/11 from a lung condition which was linked to exposure to dust during the collapse of the World Trade Center. Leon Heyward, who died of lymphoma in 2008, was added to the official death toll in 2009.

NIST estimated that about 17,400 civilians were in the World Trade Center complex at the time of the attacks, while turnstile counts from the Port Authority suggest that 14,154 people were typically in the Twin Towers by 8:45 a.m.

The vast majority of people below the impact zone safely evacuated the buildings, along with 18 people who were in the impact zone in the south tower and a number above the impact zone who evidently used the one intact stairwell in the south tower. At least 1,366 people died who were at or above the floors of impact in the North Tower and at least 618 in the South Tower, where evacuation had begun before the second impact. Thus over 90% of the workers and visitors who died in the Towers had been at or above impact.

According to the Commission Report, hundreds were killed instantly by the impact, while the rest were trapped and died after tower collapse. At least 200 people jumped to their deaths from the burning towers (as depicted in the photograph “The Falling Man”), landing on the streets and rooftops of adjacent buildings hundreds of feet below. Some of the occupants of each tower above its point of impact made their way upward toward the roof in hope of helicopter rescue, but the roof access doors were locked. No plan existed for helicopter rescues, and on September 11, the thick smoke and intense heat would have prevented helicopters from conducting rescues.

Osama bin Laden

Osama bin Laden’s declaration of a holy war against the United States, and a fatwa signed by bin Laden and others calling for the killing of American civilians in 1998, are seen by investigators as evidence of his motivation to commit such acts.

Bin Laden initially denied, but later admitted, involvement in the incidents. On September 16, 2001, bin Laden denied any involvement with the attacks by reading a statement which was broadcast by Qatar’s Al Jazeera satellite channel: “I stress that I have not carried out this act, which appears to have been carried out by individuals with their own motivation.” This denial was broadcast on U.S. news networks and worldwide.

In November 2001, U.S. forces recovered a videotape from a destroyed house in Jalalabad, Afghanistan, in which Osama bin Laden is talking to Khaled al-Harbi. In the tape, bin Laden admits foreknowledge of the attacks. The tape was broadcast on various news networks from December 13, 2001. His distorted appearance on the tape has been attributed to tape transfer artifact.

The detailed timeline of Bin Laden’s having prior knowledge were revealed in a September 2002 interview documentary-maker Yosri Fouda conducted with Khalid Sheikh Mohammed and Ramzi Binalshibh: the decision to launch a “martyrdom operation inside America” was made by Al Qaeda’s military committee in early 1999; Atta, after deciding on the date (9/11/01) for the attacks, informed Binalshibh of this date on August 29, 2001, and Bin Laden was given this information on September 6, 2001.

On December 27, 2001, a second bin Laden video was released. In the video, he states, “Terrorism against America deserves to be praised because it was a response to injustice, aimed at forcing America to stop its support for Israel, which kills our people”, but he stopped short of admitting responsibility for the attacks.

Shortly before the U.S. presidential election in 2004, in a taped statement, bin Laden publicly acknowledged al-Qaeda’s involvement in the attacks on the U.S. and admitted his direct link to the attacks. He said that the attacks were carried out because “we are free…and want to regain freedom for our nation.

As you undermine our security we undermine yours.” Osama bin Laden says he had personally directed his followers to attack the World Trade CenterIn the video, he says, “We had agreed with the Commander-General Muhammad Atta, Allah have mercy on him, that all the operations should be carried out within 20 minutes, before Bush and his administration notice.” Another video obtained by Al Jazeera in September 2006 shows Osama bin Laden with Ramzi Binalshibh, as well as two hijackers, Hamza al-Ghamdi and Wail al-Shehri, as they make preparations for the attacks

Rebuilding

On the day of the attacks, New York City mayor Rudy Giuliani proclaimed, “We will rebuild. We’re going to come out of this stronger than before, politically stronger, economically stronger. The skyline will be made whole again.” The Lower Manhattan Development Corporation, tasked with coordinating rebuilding efforts at the World Trade Center site, was criticized for doing little with the enormous funding directed to the rebuilding efforts.

Aside from construction of 7 World Trade Center, adjacent to the main site and completed in 2006, and the PATH station, which opened in late 2003, work on rebuilding on the main World Trade Center site was delayed until late 2006 when leaseholder Larry Silverstein and the Port Authority of New York and New Jersey came to an agreement on financing of the new buildings. The 1 World Trade Center is currently under construction at the site and at 1,776 ft (541 m) upon completion in 2011, will become one of the tallest buildings in North America, behind only the CN Tower in Toronto.

Three more towers were expected to be built between 2007 and 2012 on the site, and will be located one block east of where the original towers stood. After the late-2000s recession, the site’s owners said that construction of new towers could be delayed until 2036. The damaged section of the Pentagon was rebuilt and occupied within a year of the attacks.

Motives The motives for the attacks include the presence of the U.S. in Saudi Arabia, the support of Israel by the U.S., and the sanctions against Iraq.These motives were explicitly stated by Al-Qaeda in proclamations before the attacks, including the fatwa of August 1996, and a shorter fatwa published in February 1998.

After the attacks, bin Laden and al-Zawahiri published additional video tapes and audio tapes, some of which repeated those reasons for the attacks. Two particularly important publications were bin Laden’s 2002 “Letter to America”,and a 2004 video tape by bin Laden. In addition to direct pronouncements by bin Laden and Al-Qaeda, numerous political analysts have postulated motivations for the attacks.

The continued presence of U.S. troops after the Gulf War in Saudi Arabia was one of the stated motivations behind the September 11th terrorist attacks, the Khobar Towers bombing, as well, the date chosen for the 1998 United States embassy bombings (August 7), was eight years to the day that American troops were sent to Saudi Arabia. Bin Laden interpreted the Prophet Muhammad as banning the “permanent presence of infidels in Arabia”.In 1996, Bin Laden issued a fatwa, calling for American troops to get out of Saudi Arabia. In the 1998 fatwa, Al-Qaeda wrote ” for over seven years the United States has been occupying the lands of Islam in the holiest of places, the Arabian Peninsula, plundering its riches, dictating to its rulers, humiliating its people, terrorizing its neighbors, and turning its bases in the Peninsula into a spearhead through which to fight the neighboring Muslim peoples.”

In the December 1999 interview with Rahimullah Yusufzai, bin Laden said he felt that Americans were “too near to Mecca” and considered this a provocation to the entire Muslim world. In his November 2002 “Letter to America”, Bin Laden described the United States’ support of Israel as a motivation: “The creation and continuation of Israel is one of the greatest crimes, and you are the leaders of its criminals. And of course there is no need to explain and prove the degree of American support for Israel.

The creation of Israel is a crime which must be erased. Each and every person whose hands have become polluted in the contribution towards this crime must pay its price, and pay for it heavily.” In 2004 and 2010, Bin Laden again repeated the connection between the September 11 attacks and the support of Israel by the United States. Several analysts, including Mearsheimer and Walt, also assert that a motivation for the attacks was the support of Israel by the United States.

In the 1998 fatwa, Al Qaeda identified the Iraq sanctions as a reason to kill Americans: “despite the great devastation inflicted on the Iraqi people by the crusader-Zionist alliance, and despite the huge number of those killed, which has exceeded 1 million… despite all this, the Americans are once against trying to repeat the horrific massacres, as though they are not content with the protracted blockade imposed after the ferocious war or the fragmentation and devastation….On that basis, and in compliance with Allah’s order, we issue the following fatwa to all Muslims: The ruling to kill the Americans and their allies—civilians and military—is an individual duty for every Muslim…”

In addition to the motives published by Al Qaeda, analysts have suggested other motives, including humiliation resulting from the Islamic world falling behind the Western world - this discrepancy made especially visible due to recent globalisation. Another speculated motive was the desire to provoke the U.S. into a broader war against the Islamic world, with the hope of motivating more allies to support Al Qaeda.