The September 11, 2001 attacks (often referred to as 9/11—pronounced "nine eleven") consisted of a series of coordinated terrorist[1] suicide attacks upon the United States, predominantly targeting civilians, carried out on Tuesday, September 11, 2001.
That morning, 19 terrorists[2] affiliated with al-Qaeda[3] hijacked four commercial passenger jet airliners. Each team of hijackers included a trained pilot. Two aircraft (United Airlines Flight 175 and American Airlines Flight 11) crashed into the World Trade Center in New York City, one plane into each tower (WTC 1 and WTC 2). Both towers collapsed within two hours, followed by WTC 7 later that day. The pilot of the third team crashed American Airlines Flight 77 into the Pentagon in Arlington County, Virginia. Passengers and members of the flight crew on the fourth aircraft (United Airlines Flight 93) attempted to retake control of their plane from the hijackers; that plane crashed into a field near the town of Shanksville in rural Somerset County, Pennsylvania. As well as the 19 hijackers, a confirmed 2,973 people died and another 24 are missing but presumed dead as a result of these attacks.