The September 11 attacks were a series of coordinated suicide attacks by al-qaeda upon the united states on september 11, 2001. On that morning, 19 al-qaeda terrorists hijacked four commercial passengers jet airliners. The hijackers intentionally crashed two of the airliners into the Twin Towers of the world trade center in the 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 the third airliner into the pentagon in Arlington, Virginia, just outside washington, D.C.