how did 9/11 happen

The events of September 11, 2001 (9/11) occurred when 19 terrorists from the Islamist extremist group al-Qaeda hijacked four commercial passenger airplanes in the United States. The hijackers intentionally crashed two planes into the Twin Towers of the World Trade Center in New York City, causing both towers to collapse within hours. A third plane was crashed into the Pentagon near Washington, DC, while the fourth plane crashed in a field in Pennsylvania after passengers intervened to stop the hijackers. This coordinated terrorist attack killed nearly 3,000 people and caused widespread devastation. The attacks led to the U.S. launching the War on Terror, including an invasion of Afghanistan aimed at dismantling al-Qaeda and removing the Taliban regime that harbored the terrorists. The attacks profoundly shaped U.S. and global policies related to security and terrorism in the two decades following 2001.