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September 11 attacks

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September 11 attacks
A montage of eight images depicting, from top to bottom, the World Trade Center towers burning, the collapsed section of the Pentagon, the impact explosion in the south tower, a rescue worker standing in front of rubble of the collapsed towers, an excavator unearthing a smashed jet engine, three frames of video depicting airplane hitting the Pentagon.
From top to bottom: the World Trade Centre burning; a section of the Pentagon collapses; Flight 175 crashes into 2 WTC; a fireman requests help at Ground Zero; an engine from Flight 93 is recovered; Flight 77 crashes into the Pentagon.
Location New York City; Arlington County, Virginia; and near Shanksville, Pennsylvania.
Date Tuesday, September 11, 2001 (2001-09-11)
8:46 am – 10:28 am ( UTC-04:00)
Attack type Aircraft hijackings, mass murder, suicide attacks, terrorism
Deaths 2,996
Injured (non-fatal) More than 6,000
Perpetrators al-Qaeda
(See also responsibility and hijackers)

The September 11 attacks (also referred to as September 11, September 11th, or 9/11) were a series of four coordinated terrorist attacks launched by the Islamist terrorist group al-Qaeda upon the United States in New York City and the Washington, D.C. areas on September 11, 2001. On that Tuesday morning, 19 al-Qaeda terrorists hijacked four passenger jets, intending to fly them in suicide attacks into targeted buildings. Two of those planes, American Airlines Flight 11 and United Airlines Flight 175, were crashed into the North and South towers, respectively, of the World Trade Centre complex in New York City. Both towers collapsed within two hours and falling debris, combined with fires that the debris initiated in several surrounding buildings, led to the partial or complete collapse of all the other buildings in the World Trade Centre complex, also causing major damage to ten other large structures in the immediate area of the complex. A third plane, American Airlines Flight 77, was crashed into the Pentagon (the headquarters of the United States Department of Defense), leading to a partial collapse in its western side. The fourth plane, United Airlines Flight 93, was targeted at the United States Capitol in Washington, D.C., but crashed into a field near Shanksville, Pennsylvania after its passengers tried to overcome the hijackers. Almost 3,000 people died in the attacks, including all 227 civilians and 19 hijackers aboard the four planes.

Suspicion quickly fell on al-Qaeda, and in 2004, the group's leader, Osama bin Laden, who had initially denied involvement, claimed responsibility for the attacks. Al-Qaeda and bin Laden cited U.S. support of Israel, the presence of U.S. troops in Saudi Arabia, and sanctions against Iraq as motives for the attacks. The United States responded to the attacks by launching the War on Terror and invading Afghanistan to depose the Taliban, which had harbored al-Qaeda. Many countries strengthened their anti-terrorism legislation and expanded law enforcement powers. Having evaded capture for years, bin Laden was located and killed by U.S. forces in May 2011.

The destruction of the Twin Towers and other properties caused serious damage to the economy of Lower Manhattan and had a significant effect on global markets. Cleanup of the World Trade Centre site was completed in May 2002, and the Pentagon was repaired within a year. Numerous memorials have been constructed, including the National September 11 Memorial & Museum in New York, the Pentagon Memorial, and the Flight 93 National Memorial in Pennsylvania. After a lengthy delay, the 1,776-foot-tall (541 m) One World Trade Centre is expected to be completed at Ground Zero in New York City in 2013.


The flight paths of the four hijacked planes used in the terrorist attacks of September 11, 2001

Early on the morning of September 11, 2001, 19 hijackers took control of four commercial airliners (two Boeing 757 and two Boeing 767) en route to California (three headed to LAX in Los Angeles, and one to San Francisco) after takeoffs from Boston, Massachusetts; Newark, New Jersey; and Washington, D.C. Large planes with long flights were intentionally selected for hijacking because they would be heavily fueled.

The four flights were:

  • American Airlines Flight 11: Left Boston's Logan Airport at 7:59 a.m. enroute to Los Angeles with a crew of 11 and 76 passengers, not including five hijackers. The hijackers flew the plane into the North Tower of the World Trade Centre at 8:46 a.m.
  • United Airlines Flight 175: Left Logan Airport at 8:14 a.m. enroute to Los Angeles with a crew of nine and 51 passengers, not including five hijackers. The hijackers flew the plane into the South Tower of the World Trade Centre at 9:03 a.m.
  • American Airlines Flight 77: Left Washington Dulles International Airport in Virginia at 8:20 a.m. enroute to Los Angeles with a crew of six and 53 passengers, not including five hijackers. The hijackers flew the plane into the Pentagon at 9:37 a.m.
  • United Airlines Flight 93: Left Newark International Airport at 8:42 a.m. enroute to San Francisco, with a crew of seven and 33 passengers, not including four hijackers. After the passengers revolted, the hijackers crashed the plane into the ground near Shanksville, Pennsylvania at 10:03 a.m.

Media coverage was intense during the attacks and aftermath, beginning moments after the first crash into the World Trade Centre.


At 8:46 a.m., five hijackers crashed American Airlines Flight 11 into the World Trade Centre's North Tower (1 WTC), and at 9:03 a.m., another five hijackers crashed United Airlines Flight 175 into the South Tower (2 WTC). Five hijackers flew American Airlines Flight 77 into the Pentagon at 9:37 a.m.

A fourth flight, United Airlines Flight 93, under the control of four hijackers, crashed near Shanksville, Pennsylvania, southeast of Pittsburgh, at 10:03 a.m. after the passengers fought the hijackers. Flight 93's target is believed to have been either the Capitol or the White House. Flight 93's cockpit voice recorder revealed crew and passengers tried 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. Once it became evident to the hijackers that the passengers might regain control of the plane, the hijackers rolled the plane and intentionally crashed it.

The north face of Two World Trade Centre (south tower) immediately after being struck by United Airlines Flight 175

Some passengers and crew members who called from the aircraft using the cabin airphone service and mobile phones provided details: several hijackers aboard each plane; they used mace, tear gas, or pepper spray to overcome attendants; and some people aboard had been stabbed. Reports indicated hijackers stabbed and killed pilots, flight attendants, and one or more passengers. In their final report, the 9/11 Commission found the hijackers had recently purchased multi-function hand tools and assorted knives and blades. 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.

Three buildings in the World Trade Centre complex collapsed due to fire-induced structural failure. The South Tower collapsed at 9:59 a.m. after burning for 56 minutes in a fire caused by the impact of United Airlines Flight 175 and the explosion of its fuel. The North Tower collapsed at 10:28 a.m. after burning for 102 minutes. When the North Tower collapsed, debris fell on the nearby 7 World Trade Centre building (7 WTC), damaging it and starting fires. These fires burned for hours, compromising the building's structural integrity, and 7 WTC collapsed at 5:21 p.m. The Pentagon sustained major damage.

Security camera footage of Flight 77 hitting the Pentagon. The plane hits the Pentagon approximately 86 seconds after the beginning of this recording.

At 9:40 a.m., the FAA grounded all aircraft within the continental U.S., and aircraft already in flight were told to land immediately. All international civilian aircraft were either turned back or redirected to airports in Canada or Mexico, and all international flights were banned from landing on U.S. soil for three days. The attacks created widespread confusion among news organizations and air traffic controllers. Among the unconfirmed and often contradictory news reports aired throughout the day, one of the most prevalent said a car bomb had been detonated at the U.S. State Department's headquarters in Washington, D.C. 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.

In a September 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. During the planning stage of the attacks, Mohamed Atta, the hijacker and pilot of Flight 11, thought the White House might be too tough a target and sought an assessment from Hani Hanjour, who would later hijack and pilot Flight 77. Mohammed said al-Qaeda initially planned to target nuclear installations rather than the World Trade Centre and the Pentagon, but decided against it, fearing things could "get out of control." Final decisions on targets, according to Mohammed, were left in the hands of the pilots.


The remains of 6 World Trade Centre, 7 World Trade Centre, and 1 World Trade Centre on September 17, 2001

The attacks resulted in the deaths of 2,996 people, including the 19 hijackers and 2,977 victims. The victims included 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. Nearly all of the victims were civilians; 55 military personnel were among those killed at the Pentagon.

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 1,355 people at or above the point of impact were trapped and died of smoke inhalation, fell or jumped from the tower to escape the smoke and flames, or were killed in the building's eventual collapse. The destruction of all three staircases in the tower when Flight 11 hit made it impossible for anyone above the impact zone to escape. One hundred-seven people below the point of impact died as well.

In the South Tower, one stairwell (A), was left intact after Flight 175 hit, allowing 14 people located on the floors of impact (including one man who saw the plane coming at him) and four more from the floors above to escape. 911 operators who received calls from individuals 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. 630 people died in that tower, fewer than half the number killed in the North Tower. Casualties in the South Tower were significantly reduced by some occupants deciding to start evacuating as soon as the North Tower was struck.

The remaining lower part of the World Trade Centre in New York City

At least 200 people fell or jumped to their deaths from the burning towers (as exemplified in the photograph The Falling Man), landing on the streets and rooftops of adjacent buildings hundreds of feet below. Some occupants of each tower above the point of impact made their way toward the roof in hope of helicopter rescue, but the roof access doors were locked. No plan existed for helicopter rescues, and the combination of roof equipment and thick smoke and intense heat prevented helicopters from approaching. A total of 411 emergency workers died as they tried to rescue people and fight fires. The New York City Fire Department (FDNY) lost 340 firefighters, a chaplain and two paramedics. The New York City Police Department (NYPD) lost 23 officers. The Port Authority Police Department lost 37 officers. Eight emergency medical technicians (EMTs) and paramedics from private emergency medical services units were killed.

Cantor Fitzgerald L.P., an investment bank on the 101st–105th floors of the North Tower, lost 658 employees, considerably more than any other employer. Marsh Inc., located immediately below Cantor Fitzgerald on floors 93–100, lost 358 employees, and 175 employees of Aon Corporation were also killed. The National Institute of Standards and Technology (NIST) estimated that about 17,400 civilians were in the World Trade Centre complex at the time of the attacks. Turnstile counts from the Port Authority suggest 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.

After New York, New Jersey lost the most state citizens, with the city of Hoboken sustaining the most deaths. More than 90 countries lost citizens in the attacks on the World Trade Center. Two people were added to the official death toll after dying from health conditions linked to exposure to dust from the collapse of the World Trade Centre.

Deaths (+ hijackers)
New York City World Trade Centre 2,606
American 11 87 + 5
United 175 60 + 5
Arlington Pentagon 125
American 77 59 + 5
Shanksville United 93 40 + 4
Total 2,977 + 19

Weeks after the attack, the death toll was estimated to be over 6,000, more than twice the number of deaths eventually confirmed. The city was only able to identify remains for about 1,600 of the World Trade Centre 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". Bone fragments were still being found in 2006 by workers who were preparing to demolish the damaged Deutsche Bank Building. In 2010, a team of anthropologists and archaeologists searched for human remains and personal items at the Fresh Kills Landfill, where seventy-two more human remains were recovered, bringing the total found to 1,845. DNA profiling continues in an attempt to identify additional victims. As of August 2011, 1,631 victims have been identified, while 1,122 (41%) of the victims remained unidentified. The remains are being held in storage in Memorial Park, outside the New York City Medical Examiner’s facilities. It is expected that the remains will be moved in 2013 to a repository behind a wall at the 9/11 museum. As of July 2011, a team of scientists at the Office of Chief Medical Examiner continues to try to identify remains, in the hope that improved technology will allow them to identify other victims.


The Pentagon was damaged by fire and partly collapsed

Along with the 110-floor Twin Towers, numerous other buildings at the World Trade Centre site were destroyed or badly damaged, including WTC buildings 3 through 7 and St. Nicholas Greek Orthodox Church. The North Tower, South Tower, the Marriott Hotel (3 WTC) and 7 WTC were completely destroyed. The U.S. Customs House ( 6 World Trade Centre), 4 World Trade Centre, 5 World Trade Centre, and both pedestrian bridges connecting buildings were severely damaged. The Deutsche Bank Building on 130 Liberty Street was partially damaged and demolished later. The two buildings of the World Financial Centre also suffered damage.

The Deutsche Bank Building across Liberty Street from the World Trade Centre complex was later condemned as uninhabitable because of toxic conditions inside the office tower, and was deconstructed. The Borough of Manhattan Community College's Fiterman Hall at 30 West Broadway was condemned due to extensive damage in the attacks, and is being rebuilt. Other neighboring buildings including 90 West Street and the Verizon Building suffered major damage but have been restored. World Financial Centre buildings, One Liberty Plaza, the Millenium Hilton, and 90 Church Street had moderate damage and have since been restored. Communications equipment on top of the North Tower was also destroyed, but media stations were quickly able to reroute signals and resume broadcasts.

The Pentagon was severely damaged by the impact of American Airlines Flight 77 and ensuing fires, causing one section of the building to collapse. As it approached the Pentagon, the airplane's wings knocked over light poles and its right engine smashed into a power generator before crashing into the western side of the building, killing all 53 passengers, 5 hijackers, and 6 crew. 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. Debris from the tail section penetrated furthest into the building, breaking through 310 feet (94 m) of the three outermost of the building's five rings.

Rescue and recovery

 An injured victim is being loaded into a paramedic van with the burning Pentagon in the background
An injured victim of the Pentagon attack is evacuated

The New York City Fire Department deployed 200 units (half of the department) to the site. Their efforts were supplemented by numerous off-duty firefighters and emergency medical technicians. The New York City Police Department sent Emergency Service Units and other police personnel, and deployed its aviation unit. Once on the scene, the FDNY, NYPD, and Port Authority police did not coordinate efforts and performed redundant searches for civilians. As conditions deteriorated, the NYPD aviation unit relayed information to police commanders, who issued orders for its personnel to evacuate the towers; most NYPD officers were able to safely evacuate before the buildings collapsed. With separate command posts set up and incompatible radio communications between the agencies, warnings were not passed along to FDNY commanders.

After the first tower collapsed, FDNY commanders issued evacuation warnings; however, 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. Within hours of the attack, a substantial search and rescue operation was launched. After months of around-the-clock operations the World Trade Centre site was cleared by the end of May 2002.

Attackers and their background


The origins of al-Qaeda can be traced to 1979 when the Soviet Union invaded Afghanistan. Osama bin Laden traveled to Afghanistan and helped organize Arab mujahideen to resist the Soviets. Under the guidance of Ayman al-Zawahiri, bin Laden became more radical. In 1996 bin Laden issued his first fatwā, calling for American soldiers to leave Saudi Arabia.

In a second fatwā in 1998, bin Laden outlined his objections to American foreign policy with respect to Israel, as well as the continued presence of American troops in Saudi Arabia after the Gulf War. Bin Laden used Islamic texts to exhort Muslims to attack Americans until the stated grievances are reversed, and according to bin Laden, Muslim legal scholars, "have throughout Islamic history unanimously agreed that the jihad is an individual duty if the enemy destroys the Muslim countries."

Osama bin Laden

1997 picture of Osama bin Laden

Bin Laden, who orchestrated the attacks, initially denied but later admitted involvement. Al Jazeera broadcast a statement by bin Laden on September 16, 2001, stating, "I stress that I have not carried out this act, which appears to have been carried out by individuals with their own motivation." In November 2001, U.S. forces recovered a videotape from a destroyed house in Jalalabad, Afghanistan. In the tape, bin Laden is seen talking to Khaled al-Harbi and admits foreknowledge of the attacks. On December 27, 2001, a second bin Laden video was released. In the video, he said, "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." Bin Laden said he had personally directed his followers to attack the World Trade Centre. Another video obtained by Al Jazeera in September 2006 shows bin Laden with Ramzi bin al-Shibh, as well as two hijackers, Hamza al-Ghamdi and Wail al-Shehri, as they make preparations for the attacks. The U.S. never formally indicted bin Laden for the 9/11 attacks but he was on the FBI's Most Wanted List for the bombings of the U.S. Embassies in Dar es Salaam, Tanzania, and Nairobi, Kenya. After a nearly 10-year manhunt, bin Laden was killed by American special forces in a compound in Abbottabad, Pakistan on May 2, 2011.

Khalid Sheikh Mohammed

Khalid Sheikh Mohammed after his capture in 2003

The journalist Yosri Fouda of the Arabic television channel Al Jazeera reported that in April 2002, Khalid Sheikh Mohammed admitted his involvement, along with Ramzi bin al-Shibh. The 9/11 Commission Report determined that the animosity towards the United States felt by Mohammed, the principal architect of the 9/11 attacks, stemmed from his "violent disagreement with U.S. foreign policy favoring Israel".

Mohammed was also an adviser and financier of the 1993 World Trade Centre bombing and the uncle of Ramzi Yousef, the lead bomber in that attack.

Mohammed was arrested on March 1, 2003, in Rawalpindi, Pakistan by Pakistani security officials working with the CIA, then transported to Guantanamo Bay and interrogated using methods including waterboarding. During U.S. hearings at Guantanamo Bay in March 2007, Mohammed again confessed his responsibility for the attacks, stating he "was responsible for the 9/11 operation, from A to Z" and that his statement was not made under duress.

Other al-Qaeda members

In "Substitution for Testimony of Khalid Sheikh Mohammed" from the trial of Zacarias Moussaoui, five people are identified as having been completely aware of the operation's details. They are bin Laden, Khalid Sheikh Mohammed, Ramzi bin al-Shibh, Abu Turab al-Urduni and Mohammed Atef. To date, only peripheral figures have been tried or convicted for the attacks.

On September 26, 2005, the Spanish high court sentenced Abu Dahdah to 27 years in prison for conspiracy on the 9/11 attacks and being a member of the terrorist organization al-Qaeda. At the same time, another 17 al-Qaeda members were sentenced to penalties of between six and eleven years. On February 16, 2006, the Spanish Supreme Court reduced the Abu Dahdah penalty to 12 years because it considered that his participation in the conspiracy was not proven.

Also in 2006, Moussaoui, who some originally suspected might have been the assigned 20th hijacker, was convicted for the lesser role of conspiracy to commit acts of terrorism and air piracy. He is serving a life sentence without parole. Mounir el-Motassadeq, an associate of the Hamburg-based hijackers, is serving 15 years for his role in helping the hijackers prepare for the attacks.

The Hamburg cell in Germany included radical Islamists who eventually came to be key operatives in the 9/11 attacks. Mohamed Atta, Marwan al-Shehhi, Ziad Jarrah, Ramzi bin al-Shibh, and Said Bahaji were all members of al-Qaeda's Hamburg cell.


Osama bin Laden's declaration of a holy war against the United States, and a fatwā signed by bin Laden and others calling for the killing of American civilians in 1998, are seen by investigators as evidence of his motivation. In various pronouncements before and after the attacks, al-Qaeda explicitly cited three motives for its activities against Western countries: the presence of U.S. troops in Saudi Arabia, U.S. support of Israel, and sanctions against Iraq. After the attacks, bin Laden and al-Zawahiri released 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.

Bin Laden interpreted the Prophet Muhammad as having banned the "permanent presence of infidels in Arabia". In 1996, bin Laden issued a fatwā calling for American troops to leave Saudi Arabia. In 1998, 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 a December 1999, interview, bin Laden said he felt that Americans were "too near to Mecca", and considered this a provocation to the entire Muslim world. One analysis of suicide terrorism suggested that without U.S. troops in Saudi Arabia, al-Qaeda likely would not have been able to get people to commit suicide in this way.

In his November 2002 "Letter to America", bin Laden cited 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 connected the September 11 attacks with U.S. support of Israel. Bin Laden claimed in 2004 that the idea of destroying the towers had first occurred to him in 1982, when he witnessed Israel's bombardment of high-rise apartment buildings during the invasion of Lebanon. Several analysts, including Mearsheimer and Walt, also say one motivation for the attacks was U.S. support of Israel. In the 1998 fatwā, al-Qaeda identified the Iraq sanctions as a reason to kill Americans, condemning the "protracted blockade" among other actions constituting a declaration of war against "Allah, his messenger, and Muslims."

In addition to those cited by bin Laden and al-Qaeda, analysts have suggested other motives, including western support of non-Islamist authoritarian regimes in Saudi Arabia, Iran, Iraq, Pakistan and northern Africa, and western troops in some of these countries. Other authors suggest that humiliation resulting from the Islamic world falling behind the Western world – this discrepancy made especially visible by recent globalization – and a desire to provoke the U.S. into a broader war against the Islamic world, in the hope of motivating more allies to support al-Qaeda. Others have argued that 9/11 was a strategic way to provoke America into a war that incites a pan-Islamic revolution.

Events before the attacks

Planning of the attacks

ground zero and surrounding area as seen from directly above depicting where the two planes impacted the towers
Map showing the attacks on the World Trade Centre (the planes are not drawn to scale)
Diagram showing the attacks on the World Trade Centre

The idea for the attacks came from Khalid Sheikh Mohammed, who first presented it to Osama bin Laden in 1996. At that time, bin Laden and al-Qaeda were in a period of transition, having just relocated back to Afghanistan from Sudan. The 1998 African Embassy bombings and bin Laden's 1998 fatwā marked a turning point, as bin Laden became intent on attacking the United States.

In late 1998 or early 1999, bin Laden gave approval for Mohammed to go forward with organizing the plot. A series of meetings occurred in early 1999, involving Mohammed, bin Laden, and his deputy Mohammed Atef. Atef provided operational support for the plot, including target selections and helping arrange travel for the hijackers. Bin Laden overruled Mohammed, rejecting some potential targets such as the U.S. Bank Tower in Los Angeles because, "there was not enough time to prepare for such an operation".

Bin Laden provided leadership and financial support for the plot, and was involved in selecting participants. Bin Laden initially selected Nawaf al-Hazmi and Khalid al-Mihdhar, both experienced jihadists who had fought in Bosnia. Hazmi and Mihdhar arrived in the United States in mid-January 2000. In spring 2000, Hazmi and Mihdhar took flying lessons in San Diego, California, but both spoke little English, did poorly with flying lessons, and eventually served as secondary – or "muscle" – hijackers.

In late 1999, a group of men from Hamburg, Germany arrived in Afghanistan, including Mohamed Atta, Marwan al-Shehhi, Ziad Jarrah, and Ramzi bin al-Shibh. Bin Laden selected these men because they were educated, could speak English, and had experience living in the west. New recruits were routinely screened for special skills and al-Qaeda leaders consequently discovered that Hani Hanjour already had a commercial pilot's license.

Hanjour arrived in San Diego on December 8, 2000, joining Hazmi. They soon left for Arizona, where Hanjour took refresher training. Marwan al-Shehhi arrived at the end of May 2000, while Atta arrived on June 3, 2000, and Jarrah arrived on June 27, 2000. Bin al-Shibh applied several times for a visa to the United States, but as a Yemeni, he was rejected out of concerns he would overstay his visa and remain as an illegal immigrant. Bin al-Shibh stayed in Hamburg, providing coordination between Atta and Mohammed. The three Hamburg cell members all took pilot training in South Florida.

In spring 2001, the secondary hijackers began arriving in the United States. In July 2001, Atta met with bin al-Shibh in Spain, where they coordinated details of the plot, including final target selection. Bin al-Shibh also passed along bin Laden's wish for the attacks to be carried out as soon as possible.


Military operations following the attacks

At 2:40 p.m. in the afternoon of September 11, Secretary of Defense Donald Rumsfeld was issuing rapid orders to his aides to look for evidence of Iraqi involvement. According to notes taken by senior policy official Stephen Cambone, Rumsfeld asked for, "Best info fast. Judge whether good enough hit S.H." (Saddam Hussein) "at same time. Not only UBL" (Osama bin Laden). Cambone's notes quoted Rumsfeld as saying, "Need to move swiftly – Near term target needs – go massive – sweep it all up. Things related and not."

The NATO council declared the attacks on the United States were an attack on all NATO nations which satisfied Article 5 of the NATO charter. This marked the first invocation of Article 5, which had been written during the Cold War with an attack by the Soviet Union in mind. Australian Prime Minister John Howard who was in Washington D.C. during the attacks invoked Article IV of the ANZUS treaty. The Bush administration announced a War on Terror, with the stated goals of bringing bin Laden and al-Qaeda to justice and preventing the emergence of other terrorist networks. These goals would be accomplished by imposing economic and military sanctions against states perceived as harboring terrorists, and increasing global surveillance and intelligence sharing.

On September 14, 2001 a joint resolution was passed by the United States Congress authorizing U.S. Presidents to fight terrorists and the nations that harbour them called the Authorization for Use of Military Force Against Terrorists.

On October 7, 2001, the War in Afghanistan began when U.S. and British forces initiated aerial bombing campaigns targeting Taliban and al-Qaeda camps, then later invaded Afghanistan with ground troops of the Special Forces. The overthrow of the Taliban rule of Afghanistan by a U.S.-led coalition was the second-biggest operation of the U.S. Global War on Terrorism outside of the United States, and the largest directly connected to terrorism. Conflict in Afghanistan between the Taliban insurgency and the International Security Assistance Force is ongoing. The Philippines and Indonesia, among other nations with their own internal conflicts with Islamic terrorism, also increased their military readiness.

American response

At a joint session of Congress President Bush pledges to defend America's freedom against the fear of terrorism, September 20, 2001 (audio only)

Following the attacks, President Bush's approval rating soared to 90%. On September 20, 2001 he addressed the nation and a joint session of the United States Congress regarding the events of September 11 and the subsequent nine days of rescue and recovery efforts, and described his intended response to the attacks. New York City mayor Rudy Giuliani's highly visible role won him high praise in New York and nationally.

Many relief funds were immediately set up to assist victims of the attacks, with the task of providing financial assistance to the survivors of the attacks and to the families of victims. By the deadline for victim's compensation on September 11, 2003, 2,833 applications had been received from the families of those who were killed.

Contingency plans for the continuity of government and the evacuation of leaders were implemented almost immediately after the attacks. However, Congress was not told that the United States had been under a continuity of government status until February 2002.

In the largest restructuring of the U.S. government in contemporary history, the United States enacted the Homeland Security Act of 2002, creating the Department of Homeland Security. Congress also passed the USA PATRIOT Act, saying it would help detect and prosecute terrorism and other crimes. Civil liberties groups have criticized the PATRIOT Act, saying it allows law enforcement to invade the privacy of citizens and that it eliminates judicial oversight of law enforcement and domestic intelligence. In an effort to effectively combat future acts of terrorism, the National Security Agency (NSA) was given broad powers. NSA commenced warrantless surveillance of telecommunications which was sometimes criticized since it permitted the agency "to eavesdrop on telephone and e-mail communications between the United States and people overseas without a warrant".

Hate crimes

Numerous incidents of harassment and hate crimes against Muslims and South Asians were reported in the days following the 9/11 attacks. Sikhs were also targeted because Sikh males usually wear turbans, which are stereotypically associated with Muslims. There were reports of attacks on mosques and other religious buildings (including the firebombing of a Hindu temple), and assaults on people, including one murder: Balbir Singh Sodhi, a Sikh mistaken for a Muslim, was fatally shot on September 15, 2001 in Mesa, Arizona.

According to an academic study, people perceived to be Middle Eastern were as likely to be victims of hate crimes as followers of Islam during this time. The study also found a similar increase in hate crimes against people who may have been perceived as Muslims, Arabs and others thought to be of Middle Eastern origin. A report by the South Asian American advocacy group known as South Asian Americans Leading Together, documented media coverage of 645 bias incidents against Americans of South Asian or Middle Eastern descent between September 11 and 17. Various crimes such as vandalism, arson, assault, shootings, harassment, and threats in numerous places were documented.

Muslim American response

Muslim organizations in the United States were swift to condemn the attacks and called "upon Muslim Americans to come forward with their skills and resources to help alleviate the sufferings of the affected people and their families". These organizations included the Islamic Society of North America, American Muslim Alliance, American Muslim Council, Council on American-Islamic Relations, Islamic Circle of North America, and the Shari'a Scholars Association of North America. Along with monetary donations, many Islamic organizations launched blood drives and provided medical assistance, food, and shelter for victims.

International response

Vladimir Putin and his wife attending a commemoration service for the victims of the September 11 attacks, November 16, 2001

The attacks were denounced by mass media and governments worldwide. Across the globe, nations offered pro-American support and solidarity. Leaders in most Middle Eastern countries, and Afghanistan, condemned the attacks. Iraq was a notable exception, with an immediate official statement that, "the American cowboys are reaping the fruit of their crimes against humanity". While the government of Saudi Arabia officially condemned the attacks, privately many Saudis favored bin Laden's cause. As in the United States, the aftermath of the attacks saw tensions increase in other countries between Muslims and non-Muslims.

United Nations Security Council Resolution 1368 condemned the attacks, and expressed readiness to take all necessary steps to respond and combat all forms of terrorism in accordance with their Charter. Numerous countries introduced anti-terrorism legislation and froze bank accounts they suspected of al-Qaeda ties. Law enforcement and intelligence agencies in a number of countries arrested alleged terrorists.

Tens of thousands of people attempted to flee Afghanistan following the attacks, fearing a response by the United States. Pakistan, already home to many Afghan refugees from previous conflicts, closed its border with Afghanistan on September 17, 2001. Approximately one month after the attacks, the United States led a broad coalition of international forces to overthrow the Taliban regime from Afghanistan for their harboring of al-Qaeda. Though Pakistani authorities were initially reluctant to align themselves with the United States against the Taliban, they permitted the coalition access to their military bases, and arrested and handed over to the U.S. over 600 suspected al-Qaeda members.

The U.S. set up the Guantanamo Bay detention camp to hold inmates they defined as " illegal enemy combatants". The legitimacy of these detentions has been questioned by the European Union and human rights organizations.

Long-term effects

Economic aftermath

The 9/11 attacks had a major effect on the economy of New York City

The attacks had a significant economic impact on United States and world markets. The stock exchanges did not open on September 11 and remained closed until September 17. Reopening, the Dow Jones Industrial Average (DJIA) fell 684 points, or 7.1%, to 8921, a record-setting one-day point decline. By the end of the week, the DJIA had fallen 1,369.7 points (14.3%), at the time its largest one-week point drop in history. In 2001 dollars, U.S. stocks lost $1.4 trillion in valuation for the week.

In New York City, about 430,000 job-months and $2.8 billion dollars in wages were lost in the three months after the attacks. The economic effects were mainly on the economy's export sectors. The city's GDP was estimated to have declined by $27.3 billion for the last three months of 2001 and all of 2002. The U.S. government provided $11.2 billion in immediate assistance to the Government of New York City in September 2001, and $10.5 billion in early 2002 for economic development and infrastructure needs.

U.S. deficit and debt increases 2001–2008.

Also hurt were small businesses in Lower Manhattan near the World Trade Centre, 18,000 of which were destroyed or displaced, resulting in lost jobs and their consequent wages. Assistance was provided by Small Business Administration loans, federal government Community Development Block Grants, and Economic Injury Disaster Loans. Some 31,900,000 square feet (2,960,000 m2) of Lower Manhattan office space was damaged or destroyed. Many wondered whether these jobs would return, and if the damaged tax base would recover. Studies of the economic effects of 9/11 show the Manhattan office real-estate market and office employment were less affected than first feared, because of the financial services industry's need for face-to-face interaction.

North American air space was closed for several days after the attacks and air travel decreased upon its reopening, leading to a nearly 20% cutback in air travel capacity, and exacerbating financial problems in the struggling U.S. airline industry.

The September 11 attacks also led indirectly to the U.S. wars in Afghanistan and Iraq, as well as additional homeland security spending, totaling at least $5 trillion.

Health effects

Survivors were covered in dust after the collapse of the towers

Hundreds of thousands of tons of toxic debris containing more than 2,500 contaminants, including known carcinogens, were spread across Lower Manhattan due to the collapse of the Twin Towers. Exposure to the toxins in the debris is alleged to have contributed to fatal or debilitating illnesses among people who were at ground zero. The Bush administration ordered the Environmental Protection Agency (EPA) to issue reassuring statements regarding air quality in the aftermath of the attacks, citing national security, but the EPA did not determine that air quality had returned to pre-September 11 levels until June 2002.

Health effects extended to residents, students, and office workers of Lower Manhattan and nearby Chinatown. Several deaths have been linked to the toxic dust, and the victims' names were included in the World Trade Center memorial. Approximately 18,000 people have been estimated to have developed illnesses as a result of the toxic dust. There is also scientific speculation that exposure to various toxic products in the air may have negative effects on fetal development. A notable children's environmental health centre is currently analyzing the children whose mothers were pregnant during the WTC collapse, and were living or working nearby. A study of rescue workers released in April 2010 found that all those studied had impaired lung functions, and that 30–40% were reporting little or no improvement in persistent symptoms that started within the first year of the attack.

Years after the attacks, legal disputes over the costs of illnesses related to the attacks were still in the court system. On October 17, 2006, a federal judge rejected New York City's refusal to pay for health costs for rescue workers, allowing for the possibility of numerous suits against the city. Government officials have been faulted for urging the public to return to lower Manhattan in the weeks shortly after the attacks. Christine Todd Whitman, administrator of the EPA in the aftermath of the attacks, was heavily criticized by a U.S. District Judge for incorrectly saying that the area was environmentally safe. Mayor Giuliani was criticized for urging financial industry personnel to return quickly to the greater Wall Street area.

The United States Congress passed the James L. Zadroga 9/11 Health and Compensation Act on December 22, 2010, and President Barack Obama signed the act into law on January 2, 2011. It allocated $4.2 billion to create the World Trade Center Health Program, which provides testing and treatment for people suffering from long-term health problems related to the 9/11 attacks. The WTC Health Program replaced preexisting 9/11-related health programs such as the Medical Monitoring and Treatment Program and the WTC Environmental Health Centre program.

Government policies toward terrorism

As a result of the attacks, many governments across the world passed legislation to combat terrorism. In Germany, where several of the 9/11 terrorists had resided and taken advantage of that country's liberal asylum policies, two major anti-terrorism packages were enacted. The first removed legal loopholes that permitted terrorists to live and raise money in Germany. The second addressed the effectiveness and communication of intelligence and law enforcement. Canada passed the Canadian Anti-Terrorism Act, that nation's first anti-terrorism law. The United Kingdom passed the Anti-terrorism, Crime and Security Act 2001 and the Prevention of Terrorism Act 2005. New Zealand enacted the Terrorism Suppression Act 2002.

In the United States, the Department of Homeland Security was created to coordinate domestic anti-terrorism efforts. The USA Patriot Act gave the federal government greater powers, including the authority to detain foreign terror suspects for a week without charge, to monitor telephone communications, e-mail, and Internet use by terror suspects, and to prosecute suspected terrorists without time restrictions. The Federal Aviation Administration ordered that airplane cockpits be reinforced to prevent terrorists gaining control of planes, and assigned sky marshals to flights. Further, the Aviation and Transportation Security Act made the federal government, rather than airports, responsible for airport security. The law created a federal security force to inspect passengers and luggage, causing long delays and concern over passenger privacy.

Cultural impact

The impact of 9/11 extends beyond geopolitics into society and culture in general. Immediate responses to 9/11 included greater focus on home life and time spent with family, higher church attendance, and increased expressions of patriotism such as the flying of flags. The radio industry responded by removing certain songs from playlists, and the attacks have subsequently been used as background, narrative or thematic elements in film, television, music and literature. Already-running television shows as well as programs developed after 9/11 have reflected post-9/11 cultural concerns. 9/11 conspiracy theories have become social phenomena, despite negligible support for such views from expert scientists, engineers, and historians.


FBI investigation

 A head shot of a man in his thirties looking expressionless toward the camera
Mohamed Atta, an Egyptian national, was the ringleader of the hijackers.

Immediately after the attacks, the Federal Bureau of Investigation started PENTTBOM, the largest criminal inquiry in the history of the United States. At its height, more than half of the FBI's agents worked on the investigation and followed a half-million leads. The FBI concluded that there was "clear and irrefutable" evidence linking al-Qaeda and bin Laden to the attacks. The FBI was quickly able to identify the hijackers, including leader Mohamed Atta, when his luggage was discovered at Boston's Logan Airport. Due to a mix-up, the luggage failed to make it aboard American Airlines Flight 11 as planned. The luggage contained the hijackers' names, assignments and al-Qaeda connections. "It had all these Arab-language (sic) papers that amounted to the Rosetta stone of the investigation", said one FBI agent.

Within hours of the attacks, the FBI released the names and in many cases the personal details of the suspected pilots and hijackers. By midday, the U.S. National Security Agency and German intelligence agencies had intercepted communications pointing to Osama bin Laden. On September 27, 2001, the FBI released photos of the 19 hijackers, along with information about possible nationalities and aliases. Fifteen of the men were from Saudi Arabia, two from the United Arab Emirates, one (Atta) from Egypt, and one from Lebanon.

Origins of the 19 hijackers
Nationality Number
Saudi Arabia
United Arab Emirates

9/11 Commission

The National Commission on Terrorist Attacks Upon the United States (9/11 Commission), chaired by former New Jersey Governor Thomas Kean, was formed in late 2002 to prepare a thorough account of the circumstances surrounding the attacks, including preparedness for and the immediate response to the attacks. On July 22, 2004, the 9/11 Commission issued the 9/11 Commission Report. The report detailed the events of 9/11, found the attacks were carried out by members of al-Qaeda, and examined how security and intelligence agencies were inadequately coordinated to prevent the attacks. Formed from an independent bipartisan group of mostly former Senators, Representatives, and Governors, the commissioners explained, "We believe the 9/11 attacks revealed four kinds of failures: in imagination, policy, capabilities, and management". The commission made numerous recommendations on how to prevent future attacks, and in 2011 was dismayed that several of its recommendations had yet to be implemented.

Collapse of the World Trade Centre

The exterior support columns from the lower level of the south tower remained standing after the building collapsed

The U.S. National Institute of Standards and Technology investigated the collapses of the Twin Towers and 7 WTC. The investigations examined why the buildings collapsed and what fire protection measures were in place, and evaluated how fire protection systems might be improved in future construction. The investigation into the collapse of 1 WTC and 2 WTC was concluded in October 2005 and that of 7 WTC was completed in August 2008.

The NIST found that the fireproofing on the Twin Towers' steel infrastructures was blown off by the initial impact of the planes and that, had this not occurred, the towers likely would have remained standing. A 2007 study of the north tower's collapse published by researchers of Purdue University determined that, since the plane's impact had stripped off much of the structure's thermal insulation, the heat from a typical office fire would have softened and weakened the exposed girders and columns enough to initiate the collapse regardless of the number of columns cut or damaged by the impact.

The director of the original investigation stated that, "the towers really did amazingly well. The terrorist aircraft didn’t bring the buildings down; it was the fire which followed. It was proven that you could take out two thirds of the columns in a tower and the building would still stand." The fires weakened the trusses supporting the floors, making the floors sag. The sagging floors pulled on the exterior steel columns causing the exterior columns to bow inward. With the damage to the core columns, the buckling exterior columns could no longer support the buildings, causing them to collapse. Additionally, the report found the towers' stairwells were not adequately reinforced to provide adequate emergency escape for people above the impact zones. NIST concluded that uncontrolled fires in 7 WTC caused floor beams and girders to heat and subsequently "caused a critical support column to fail, initiating a fire-induced progressive collapse that brought the building down".

Internal review of the CIA

The Inspector General of the CIA conducted an internal review of the CIA's pre-9/11 performance and was harshly critical of senior CIA officials for not doing everything possible to confront terrorism. He criticized their failure to stop two of the 9/11 hijackers, Nawaf al-Hazmi and Khalid al-Mihdhar, as they entered the United States and their failure to share information on the two men with the FBI. In May 2007, senators from both major U.S. political parties drafted legislation to make the review public. One of the backers, Senator Ron Wyden said, "The American people have a right to know what the Central Intelligence Agency was doing in those critical months before 9/11."

Rebuilding and revitalization

New One World Trade Centre under construction on September 21, 2012

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 damaged section of the Pentagon was rebuilt and occupied within a year of the attacks. The temporary World Trade Center PATH station opened in late 2003 and construction of the new 7 World Trade Center was completed in 2006. Work on rebuilding the main World Trade Centre site was delayed until late 2006 when leaseholder Larry Silverstein and the Port Authority of New York and New Jersey agreed on financing. One World Trade Centre is currently under construction at the site and at 1,776 ft (541 m) upon completion in 2013, will become the tallest building in North America.

On the World Trade Center site, three more office towers are expected to be built one block east of where the original towers stood. Construction has begun on all three of these towers; they are expected to be completed after One World Trade Centre.


The Tribute in Light on September 11, 2011, on the tenth anniversary of the attacks, seen from New Jersey. The building lit up in red, white, and blue is the new One World Trade Centre under construction.

In the days immediately following the attacks, many memorials and vigils were held around the world. In addition, people posted photographs of the dead and missing all around Ground Zero. A witness described being unable to "get away from faces of innocent victims who were killed. Their pictures are everywhere, on phone booths, street lights, walls of subway stations. Everything reminded me of a huge funeral, people quiet and sad, but also very nice. Before, New York gave me a cold feeling; now people were reaching out to help each other.”

One of the first memorials was the Tribute in Light, an installation of 88 searchlights at the footprints of the World Trade Centre towers. In New York, the World Trade Centre Site Memorial Competition was held to design an appropriate memorial on the site. The winning design, Reflecting Absence, was selected in August 2006, and consists of a pair of reflecting pools in the footprints of the towers, surrounded by a list of the victims' names in an underground memorial space. Plans for a museum on the site have been put on hold, following the abandonment of the International Freedom Centre in reaction to complaints from the families of many victims.

The Pentagon Memorial was completed and opened to the public on the seventh anniversary of the attacks in 2008. It consists of a landscaped park with 184 benches facing the Pentagon. When the Pentagon was repaired in 2001–2002, a private chapel and indoor memorial were included, located at the spot where Flight 77 crashed into the building.

In Shanksville, a permanent Flight 93 National Memorial is planned to include a sculpted grove of trees forming a circle around the crash site, bisected by the plane's path, while wind chimes will bear the names of the victims. A temporary memorial is located 500 yards (457 m) from the crash site. New York City firefighters donated a cross made of steel from the World Trade Centre and mounted on top of a platform shaped like the Pentagon. It was installed outside the firehouse on August 25, 2008. Many other permanent memorials are elsewhere. Scholarships and charities have been established by the victims' families, and by many other organizations and private figures.

On every anniversary, in New York City, the names of the victims who died there are read out against a background of somber music. The President of the United States attends a memorial service at the Pentagon, and asks Americans to observe Patriot Day with a moment of silence. Smaller services are held in Shanksville, Pennsylvania, which are usually attended by the President's spouse.

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