The attacks were carried out by 19 al-Qaida terrorists, 15 from Saudi Arabia and the others from Lebanon, Egypt and United Arab Emirates, who hijacked four commercial airliners on the morning of Sept. 11, 2001.
Two of the airliners targeted the north and south towers of the World Trade Center in New York City and both towers collapsed less than two hours later. A third was crashed into the Pentagon, leading to a partial collapse of the building’s western side. The fourth initially was steered toward Washington, D.C., but crashed in a field near Shanksville, Pennsylvania, after passengers tried to overcome the hijackers.
In all, 2,996 people were killed and more than 6,000 were injured. Estimates of the total financial cost of the attacks are about $2 trillion.
Two of the terrorists who hijacked Flight 11 out of Boston and crashed it into the 110-story north tower of the trade center, Mohamed Atta and Abdulaziz Alomari, stayed at a motel in Portland the night before and flew to Boston from Portland International Jetport. Atta, federal investigators say, choreographed the attacks and piloted the airliner.