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The September 11 attacks, commonly known as 9/11, were four coordinated Islamist suicide
terrorist attacks carried out by al-Qaeda against the United States on Tuesday, September 11, 2001.
That morning, 19 terrorists hijacked four commercial airliners scheduled to travel from the New
England and Mid-Atlanticregions of the East Coast to California. The hijackers crashed the first two
planes into the Twin Towers of the World Trade Center in New York City, two of the world's five
tallest buildings at the time, and aimed the next two flights toward targets in or near Washington,
D.C., in an attack on the nation's capital. The third team succeeded in crashing into the Pentagon,
the headquarters of the U.S. Department of Defense in Arlington County, Virginia, while the fourth
plane crashed in rural Pennsylvania following a passenger revolt. The attacks killed nearly 3,000
people and instigated the multi-decade global war on terror.
The first impact was that of American Airlines Flight 11, which crashed into the North Tower of the
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World Trade Center complex in Lower Manhattan at 08:46. Sixteen minutes later, at 09:03, the
World Trade Center's South Tower was hit by United Airlines Flight 175. Both 110-story skyscrapers
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collapsed within an hour and forty-one minutes, bringing about the destruction of the remaining
five structures in the WTC complex, as well as damaging or destroying various other buildings
surrounding the towers. A third flight, American Airlines Flight 77, crashed into the Pentagon at
09:37, causing a partial collapse. The fourth and final flight, United Airlines Flight 93, flew in the
direction of the capital. Alerted to the previous attacks, the passengers retaliated in an attempt to
take control of the aircraft, forcing the hijackers to crash the plane in a Stonycreek Township field,
near Shanksville at 10:03 that morning. Investigators determined that Flight 93's target was either
the United States Capitol or the White House.
Within hours of the attacks, the Central Intelligence Agency determined that al-Qaeda was
responsible. The United States formally responded by launching the war on terror and invading
Afghanistan to depose the Taliban, which rejected the conditions of U.S. terms to expel al-Qaeda
from Afghanistan and extradite its leaders. The U.S.'s invocation of Article 5 of the North Atlantic
Treaty—its only usage to date—called upon allies to fight al-Qaeda. As U.S. and NATO invasion
forces swept through Afghanistan, al-Qaeda leader Osama bin Laden disappeared into the White
Mountains, eluding captivity by western forces. Although bin Laden initially denied any involvement,
in 2004 he formally claimed responsibility for the attacks. Al-Qaeda's cited motivations included U.S.
support of Israel, the presence of U.S. military bases in Saudi Arabia and sanctions against Iraq. The
nearly decade-long manhunt for bin Laden concluded on May 2, 2011, when he was killed during a
U.S. military raid after being tracked down to his compound in Abbottabad, Pakistan. The war in
Afghanistan continued for another eight years until the agreement was made in February 2020 for
American and NATO troops to withdraw from the country, and the last members of the U.S. armed
forces left the region on August 30, 2021, resulting in the return to power of the Taliban.