The September 11, 2001 attacks were a series of coordinated terrorist attacks against the United States on September 11, 2001. Members of the al-Qaida militant Islamist group hijacked four aircraft. They crashed two into the two towers of the World Trade Center in Manhattan, New York City and a third into the U.S. Department of Defense headquarters, the Pentagon, in Arlington County, Virginia, just outside of the capital, Washington, D.C.. A fourth hijacked plane was intentionally crashed into a field near Shanksville, Pennsylvania, after passengers fought back.
The attacks were the first highly lethal attack by a foreign force on the mainland U.S. since the War of 1812. With a death toll of nearly 3,000, the attacks exceeded the toll of approximately 2,400 dead following the surprise Japanese attack on Pearl Harbor in 1941.
The attacks involved the hijacking of four commercial airliners. With nearly 91m3 (24,000 U.S. gallons) of jet fuel aboard, the aircraft were turned into flying bombs. American Airlines Flight 11 crashed into the north side of the north tower of the WTC at 8:46:40 AM local time (12:46:40 UTC). At 9:03:11 AM local time (13:03:11 UTC), United Airlines Flight 175 crashed into the south tower. American Airlines Flight 77 crashed into the Pentagon at 9:37:46 AM local time (13:37:46 UTC). The fourth hijacked plane, United Airlines Flight 93, was crashed in a field near Shanksville and Stonycreek Township in Somerset County, Pennsylvania, at 10:03:11 AM local time (14:03:11 UTC) as the hijackers fought off a passenger revolt. No one in the hijacked aircraft survived.
The casualties were in the thousands: 265 on the planes; at least 2,602 people, including 343 firefighters, at the World Trade Center; and 125 at the Pentagon. At least 2,992 people were killed. In addition to the 110-floor Twin Towers of the World Trade Center ("WTC") itself, five other buildings at the WTC site and four underground railway stations were destroyed or badly damaged. In total, on Manhattan Island, 25 buildings were damaged. In Arlington, a portion of the Pentagon was severely damaged by fire and one section of the building collapsed.
Some passengers and crew members were able to make phone calls from the doomed flights (see Communication during the September 11, 2001 attacks). They reported that multiple hijackers were aboard each plane. A total of 19 were later identified, five on most flights and four on United 93. Reportedly, the hijackers took control of the aircraft by using knives to kill flight attendants, pilots, and/or at least one passenger. On American 77, one of the passengers reported that the hijackers used box-cutters. Some form of noxious chemical spray, such as tear gas or pepper spray, was reported to have been used on American 11 and United 175 to keep passengers out of the first-class cabin. Bomb threats were made on three planes, but not American 77.
The fourth aircraft
It has been speculated that the hijackers of the fourth hijacked aircraft, United Airlines Flight 93, intended to crash into either the U.S. Capitol or the White House in Washington, DC. Black box recordings revealed that the passengers attempted to seize control of the plane from the hijackers and when rocking the plane failed to subdue the passengers, the hijackers crashed the aircraft in a field near Shanksville and Stonycreek Township in Somerset County, Pennsylvania at 10:03:11 AM local time (14:03:11 UTC).
Main article: Significance of '9/11'
The attacks are often referred to simply as September 11 or 9/11. The latter is from the U.S. style for writing short dates, and is pronounced "nine-eleven." The day was a Tuesday, and U.S. domestic airliners carry fewer passengers in the middle of the week, thus making a plane easier to hijack.
Main article: Responsibility for the September 11, 2001 attacks
On October 29 2004, Osama bin Laden explicity took responsibility for the attacks. He stated, "We decided to destroy towers in America ... God knows that it had not occurred to our mind to attack the towers, but after our patience ran out and we saw the injustice and inflexibility of the American-Israeli alliance toward our people in Palestine and Lebanon, this came to my mind."
The militant Islamic al-Qaida group had praised the attacks and the group's leaders had previously hinted at their involvement in the incidents. Indeed, shortly after the attacks, the United States government declared them and their leader, Osama bin Laden, as the prime suspects. In 2004, the U.S. government commission investigating the attacks officially concluded that the attacks were conceived and implemented by al-Qaida operatives.  (http://www.9-11commission.gov/) The official panel investigating the attacks reported that, while contacts between Iraq under the presidency of Saddam Hussein were made, it had found no "collaborative relationship" between Iraq and al-Qaida regarding the September 11 attacks specifically; however it was found that al-Qaida did have connections with Iraqi groups dating back to the early 1990s.  (http://www.csmonitor.com/2002/0315/p01s04-wome.html)  (http://www.globalsecurity.org/wmd/library/news/iraq/2004/01/iraq-040107-rferl-163840.htm).
Military and security measures
The attacks led to what President George W. Bush has called the War on Terror or War on Terrorism. The U.S. government increased military operations, economic measures and political pressure on groups it accused of being terrorists, as well as on governments and countries accused of sheltering them. October 2001 saw the first military action initiated by the U.S. under this policy, when the U.S. removed the Taliban Government in Afghanistan, after they refused to extradite Osama bin Ladin to the U.S.. The September 11 attacks also precipitated a focus on domestic security issues and the creation of a new cabinet-level federal agency, the Department of Homeland Security.
In the immediate aftermath of the September 11 attacks, the United States and other countries around the world were placed on a high state of alert against potential follow-up attacks. Civilian air travel across the United States was—for the first time ever—suspended almost totally for three days, with numerous locations and events affected by closures, postponements, cancellations, and evacuations. Other countries imposed similar security restrictions: in the United Kingdom, for instance, civilian aircraft were forbidden to fly over London for several days after the attacks.
The attacks also had major world-wide political effects. Many countries introduced tough anti-terrorism legislation - in the U.S., the USA PATRIOT Act - and took action to cut off terrorist finances (including the freezing of bank accounts suspected of being used to fund terrorism). Law enforcement and intelligence agencies stepped up cooperation to arrest terrorist suspects and break up suspected terrorist cells around the world. This was a highly controversial process, as prior restrictions on governmental authority were lifted and certain civil rights protections were rescinded. This was highlighted in September 2004 when Yusuf Islam, a leading British Muslim noted for his peaceful charitable work and previously known as Cat Stevens, was barred from entering the U.S. This led to British foreign secretary, Jack Straw complaining to the U.S. Secretary of State, Colin Powell, who ordered a review of restrictions placed on people entering the U.S.
The attack prompted numerous memorials and services all over the world. In Berlin, 200,000 Germans marched to show their solidarity with America. The French newspaper Le Monde, typically critical of the United States Government, ran a front-page headline reading "Nous Sommes Tous Américains", or "We are all Americans". In London, the U.S. national anthem was played at the changing of the guard. In the immediate aftermath, support for the United States' right to defend itself was expressed across the world, as expressed in United Nations Security Council Resolution 1368  (http://www.state.gov/p/io/rls/othr/2001/4899.htm).
The reaction to the attacks in the Muslim world was mixed. The great majority of Muslim political and religious leaders condemned the attacks - virtually the only significant stand-out was Saddam Hussein, the then president of Iraq. Shortly after the attack there were reported popular celebrations in some countries by people opposed to U.S. policies in the Middle East.
Reaction amongst the United States population
The attacks also had immediate and overwhelming effects upon the United States population. Gratitude toward uniformed public-safety workers (especially toward firefighters) was widely expressed in light of both the drama of the risks taken on the scene and the high death toll among them. The number of casualties among the emergency services was unprecedented. The highly visible role played by Rudolph Giuliani, the Mayor of New York City, won him high praise nationally. He was named Person of the Year by Time Magazine for 2001, and at times had a higher profile in the U.S. than President George W. Bush.
The attacks had significant economic repercussions to the United States and world markets. The New York Stock Exchange, the American Stock Exchange and NASDAQ did not open on September 11 and remained closed until September 17. New York Stock Exchange (“NYSE”) facilities and remote data processing sites were not damaged by the attack but member firms, customers and markets were unable to communicate due to major damage to the telephone exchange facility near the World Trade Center. When the stock markets reopened on September 17 2001, after the longest closure since the Great Depression in 1933, the Dow Jones Industrial Average (“DJIA”) stock market index fell 684 points, or 7.1%, to 8920, its biggest-ever one-day point decline. By the end of the week the DJIA had fallen 1369.7 points (14.3%), its largest one-week point drop in history. U.S. stocks lost $1.2 trillion in value for the week.
Insurance claims and claims against the airlines
The terrorist attack on the World Trade Center has led to the largest-ever terrorism-related insurance claims, with many insurance companies throughout the world having to disclose the impact of the attack in their financial statements. In April 2004, a U.S. District Court jury rejected claims by World Trade Center leaseholder, Larry Silverstein, that two planes hitting the Twin Towers should within the terms of his insurance policies be considered two separate incidents, which would have entitled him to $7 billion in insurance reimbursements. The insurers, Swiss Reinsurance Co. and others, successfully argued that the attacks in New York were one incident and that Silverstein is only entitled to $3.5 billion.
In 2003, U.S. District Judge Alvin Hellerstein agreed to hear a consolidated master case against three airlines, ICTS International NV and Pinkerton's airport security firms, the World Trade Center owners and Boeing Co., the aircraft manufacturer. The case was brought by people injured in the attacks, representatives of those who died and entities that suffered property damage. In September 2004, just prior to the expiration of a three-year statute of limitations, the insurers for the World Trade Center filed suit against American Airlines, United Airlines, and Pinkerton's airport security firm, alleging their negligence allowed the planes to be hijacked. Because the Air Transportation Act passed after the September 11 attacks limits the liability of airlines, plane manufacturers and airports to the amount of their insurance coverage, this case will likely be combined with the consolidated master case filed in 2003.
Rescue and recovery
Rescue and recovery efforts took months to complete. It took weeks simply to put out the fires burning in the rubble of the WTC and the clean-up was not completed until May 2002. Many relief funds were immediately set up to assist victims of the attacks. The task of providing financial assistance to the survivors and the families of victims is still ongoing.
A small number of survivors and surprisingly few intact victims' remains were found in the rubble of the WTC. The forces unleashed by the towers' disintegration were so great that many of those trapped in the buildings were simply pulverized in the collapse. Some victims had to be identified by as little as a few scraps of flesh or individual teeth. Most bodies were never found at all, presumably because the heat of the fires had completely incinerated them. On January 18, 2002, the last hospitalized survivor of the World Trade Center attack was released from hospital.
Over 1.5 million tons of debris produced by the collapse of the WTC posed unique problems for the cleanup effort. A fully occupied skyscraper had never previously collapsed and the environmental and health consequences of such an event were unknown. About 100 tons of asbestos used in the construction of the WTC had not yet been fully removed  (http://asbnyc.cjb.net/). The attacks released dense clouds of dust containing pulverized cement, glass fibers, asbestos, and other airborne contaminants. By 2004, nearly half of more than 1,000 screened rescue and recovery workers and volunteers reported new and persistent respiratory problems and more than half reported persistent psychological symptoms.  (http://www.cdc.gov/od/oc/media/pressrel/r040909.htm) Because of the long latency period between exposure and development of asbestos-related diseases, exposed Manhattan residents, especially rescue and recovery workers, may suffer future adverse health effects.
Six months after the attack, the 1.5 million tons of debris had been removed from the WTC site and work continued below ground level, despite concerns that the slurry wall encompassing the site foundation (known as the Bathtub) might collapse. Ceremonies marking the completion of debris removal took place at the end of May 2002.
Collapse of the World Trade Center
Main article: Collapse of the World Trade Center
There has been much speculation as to why the Twin Towers of the WTC collapsed, and the reason for the collapse is under active debate by structural engineers, architects and the relevant U.S. government agencies. Certainly the force of the jetliner impacts was unprecedented outside the battlefield, as was the intense heat of the resulting fires that were fed by 91m3 (24,000 U.S. gallons) of jet fuel. But the WTC design, with its non-traditional, lightweight, largely hollow configuration may have been, in some ways, more prone to penetration, fire damage, and structural failure than an older construction.
Speculation and conspiracy theories
Since the attacks there has been much speculation concerning their planning, especially concerning whether there were any more planned hijackers. Many conspiracy theories also surround the attacks.
Twenty-seven members of al-Qaida attempted to enter the United States to take part in the September 11 attacks. In the end, only nineteen participated. Other would-be hijackers are often referred to as "20th hijacker"s.
Binalshibh meant to take part in the attacks, but he was repeatedly denied entry into the U.S. Mohamed al-Kahtani was another would-be hijacker, but he was denied entry into the U.S. at Orlando International Airport in August 2001. He was later captured and imprisoned at Guantanamo Bay. Zacarias Moussaoui was considered as a replacement for Ziad Jarrah, who at one point threatened to withdraw from the scheme because of tensions amongst the plotters. Plans to include Moussaoui were never completed, as the al-Qaida hierarchy had doubts about his reliability. Ultimately, Moussaoui did not play a role in the hijacking scheme.
The other al-Qaida members who attempted to take part in the attacks, but were not able, were Saeed al-Ghamdi (not to be confused with the successful hijacker of the same name), Mushabib al-Hamlan, Zakariyah Essabar, Ali Abdul Aziz Ali, and Tawfiq bin Attash. Khalid Sheikh Mohammed, the attack's mastermind, had wanted to remove at least one member -- Khalid al-Mihdhar -- from the operation, but he was overruled by Osama bin Laden.
ar:11_سبتمبر_2001 da:Terrorangrebet den 11. september 2001 de:Terroranschläge am 11. September 2001 in den USA eo:11-a de septembro 2001 es:Atentados del 11 de septiembre de 2001 fr:11 septembre 2001 he:פיגועי ה-11 בספטמבר it:11 Settembre 2001 ja:アメリカ同時多発テロ事件 nl:11 september 2001 ko:11일9월 공격 pl:Zamach na World Trade Center i Pentagon simple:September 11, 2001 attacks sv:11 september 2001 zh-cn:九一一恐怖袭击事件 zh-tw:九一一恐怖襲擊事件 pt: Ataques_de_11_de_Setembro