U.S. military response during the September 11 attacks

On the morning of Tuesday, September 11, 2001, Islamist terrorist group al-Qaeda hijacked four commercial airliners in the United States and tried to crash them into large buildings, succeeding in three cases. American Airlines Flight 11, having departed from Boston, was flown into the North Tower of the World Trade Center at 08:46. United Airlines Flight 175, also leaving from Boston, struck the South Tower at 09:03. American Airlines Flight 77, from Washington Dulles International Airport, hit the Pentagon at 09:37. United Airlines Flight 93, from Newark Liberty International Airport, was crashed near Shanksville, Pennsylvania, at 10:03, after the passengers on board revolted.

Standing orders on September 11 dictated that, on receiving a request for help from the Federal Aviation Administration (FAA), the North American Aerospace Defense Command (NORAD) would normally order escort aircraft to approach and follow an aircraft that was confirmed to be hijacked in order to ensure positive flight following, report unusual observations, and help in search and rescue in an emergency.^[1] The 9/11 Commission determined that, on the morning of September 11, the FAA had not notified NORAD of the hijackings of Flights 11, 77, 93, and 175 in time for escort aircraft to reach the hijacked flights.^[2] Notification of the hijacking of Flight 11 prompted the scrambling of two fighter jets from Otis Air National Guard Base, but they were not in the air until after Flight 11 had hit the North Tower. An erroneous FAA report of a hijacked plane heading towards Washington ("phantom Flight 11") prompted the scrambling of three fighters from the 1st Fighter Wing at Langley Air Force Base, which, because of "poor communications", flew east, out to sea, not toward Washington, significantly delaying their arrival on the scene.^[2]