September 11 attacks

The September 11 attacks, colloquially known as 9/11, were four coordinated Islamist terrorist suicide attacks by al-Qaeda against the United States in 2001. Nineteen terrorists hijacked four airliners, then flew one into each of the Twin Towers at the World Trade Center in New York City. The third plane crashed into the Pentagon, the headquarters of the U.S. Department of Defense, in Arlington County, Virginia. The fourth plane crashed in a rural Pennsylvania field during a passenger revolt. In response to the attacks, the United States launched the global war on terror, seeking to eliminate hostile groups deemed terrorist organizations and the governments purported to support them over two decades.

Ringleader and hijacker Mohamed Atta flew American Airlines Flight 11 into the North Tower of the World Trade Center complex at 8:46 a.m. At 9:03 a.m., hijacker Marwan al-Shehhi flew United Airlines Flight 175 into the South Tower. Both collapsed within an hour and forty-two minutes, destroying the remaining five structures in the complex. Hijacker Hani Hanjour flew American Airlines Flight 77 into the Pentagon at 9:37 a.m., causing a partial collapse. United Airlines Flight 93, flown by hijacker Ziad Jarrah, was believed to target either the United States Capitol or the White House. Alerted to the previous attacks, the passengers revolted and the hijackers crashed the aircraft into a field near Shanksville, Pennsylvania, at 10:03 a.m. The Federal Aviation Administration ordered a ground stop for all traffic in U.S. airspace, requiring all airborne aircraft to return to their point of origin or divert to Canada. The actions undertaken in Canada to support incoming aircraft and their occupants were collectively titled Operation Yellow Ribbon.