What historical event happened on September 11 2001 in the United states?

On September 11, 2001, a series of coordinated terrorist attacks were carried out by the extremist group al-Qaeda against the United States. Four commercial airplanes were hijacked; two were flown into the Twin Towers of the World Trade Center in New York City, causing their collapse, while another struck the Pentagon in Arlington, Virginia. The fourth plane, United Airlines Flight 93, crashed in Pennsylvania after passengers attempted to overcome the hijackers. This tragic event resulted in the deaths of nearly 3,000 people and led to significant changes in U.S. domestic and foreign policy, including the initiation of the War on Terror.