The September 11 attacks, commonly known as 9/11,[d] were four coordinated suicide terrorist attacks carried out by the militant Islamist extremist network al-Qaeda[4][5][6] against the United States on Tuesday, September 11, 2001. That morning, nineteen terrorists hijacked four commercial airliners scheduled to travel from the Northeastern United States to California. The hijackers crashed the first two

planes into the Twin Towers of the World Trade Center in New York City, and the third plane into the Pentagon (the headquarters of the United States military) in Arlington County, Virginia. The fourth plane was intended to hit a federal government building[e] in Washington, D.C., but crashed in a field following a passenger revolt.[7] The attacks killed nearly 3,000 people and instigated the global war on terror.

The first impact was that of American Airlines Flight 11. It was crashed into the North Tower of the World Trade Center complex in Lower Manhattan at 8:46 a.m. Seventeen minutes later, at 9:03,[f] the World Trade Center’s South Tower was hit by United Airlines Flight 175. Both 110-story skyscrapers collapsed within an hour and forty-two minutes, precipitating the collapse of other World Trade Center structures including 7 World Trade Center, and damaging nearby buildings. A third flight, American Airlines Flight 77, crashed into the west side of the Pentagon in Arlington County, Virginia, at 9:37 a.m., causing a partial

collapse. The fourth and final flight, United Airlines Flight 93, flew in the direction of Washington, D.C. Alerted of the previous attacks, the plane's passengers fought back in an attempt to gain[g] control of the aircraft, but the hijackers ultimately crashed the plane in a field in Stonycreek Township, Pennsylvania, near Shanksville at 10:03 a.m. Investigators determined that Flight 93 was targeting either the United States Capitol or the White House.

Within hours of the attacks, suspicion quickly fell onto al-Qaeda. The United States formally responded by launching the war on terror and invading Afghanistan to depose the Taliban, which had not complied with U.S. demands to expel al-Qaeda from Afghanistan and extradite its leader, Osama bin Laden. The U.S.'s invocation of Article 5 of NATO—its only usage to date—called upon allies to fight al-Qaeda. As

U.S. and NATO ground forces swept through Afghanistan, bin Laden fled to the White Mountains, where he narrowly avoided capture by U.S.-led forces.[12] Although bin Laden initially denied any involvement, in 2004 he formally claimed responsibility for the attacks.[3] Al-Qaeda's cited motivations included U.S. support of Israel, the presence of U.S. troops in Saudi Arabia, and sanctions against Iraq. After evading capture for almost a decade, bin Laden was killed by the U.S. military on May 2, 2011.