The September 11 attacks involved airplanes.
September 11 attacks . 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 . Two of the planes , American Airlines Flight 11 and United Airlines Flight 175 , were crashed into the North and South towers , respectively , of the World Trade Center complex in New York City . A third plane , American Airlines Flight 77 , was crashed into the Pentagon ( the headquarters of the United States Department of Defense ) in Arlington County , Virginia , leading to a partial collapse of the building 's western side . The fourth plane , United Airlines Flight 93 , initially was steered toward Washington , D.C. , but crashed into a field in Stonycreek Township near Shanksville , Pennsylvania , after its passengers tried to overcome the hijackers .