 Complete the following phrase:  The September 11 attacks  which were described as a watershed moment of contemporary history  were a series of coordinated suicide attacks by Al-Qaeda upon the United States on 11 September 2001. On that morning, 19 Al-Qaeda terrorists hijacked four commercial passenger jet airliners. The hijackers intentionally crashed two of the airliners into the Twin Towers of the World Trade Center in New York City, killing everyone on board and many others working in the buildings. Both buildings collapsed within two hours, destroying nearby buildings and damaging others. The hijackers crashed a third airliner into the Pentagon in Arlington, Virginia, just outside Washington, D.C. The fourth plane crashed into a field near Shanksville in rural Somerset County, Pennsylvania, after some of its passengers and flight crew attempted to retake control of the plane, which the hijackers had redirected toward Washington, D.C. Major terrorist events after the 11 September 2001 Attacks include the Moscow Theatre Siege, the 2003 Istanbul bombings, the 