Al-Qaeda executed the September 11 attacks.
American Airlines Flight 11 was a domestic passenger flight that was hijacked by five al-Qaeda members on September 11 , 2001 , as part of the September 11 attacks . The Twin Towers of the World Trade Center collapsed on September 11 , 2001 , as a result of being struck by two jet airliners hijacked by 10 terrorists affiliated with al-Qaeda , during the September 11 attacks . September 11 attacks . were a series of four coordinated terrorist attacks by the Islamic terrorist group al-Qaeda on the United States on the morning of Tuesday , September 11 , 2001 . Four passenger airliners operated by two major U.S. passenger air carriers ( United Airlines and American Airlines ) -- all of which departed from airports in the northeastern United States bound for California -- were hijacked by 19 al-Qaeda terrorists .