On September 11, 2001, members of the terrorist group al-Qaeda hijacked four commercial airplanes in the United States. Two planes were flown into the Twin Towers of the World Trade Center in New York City, causing both towers to collapse. A third struck the Pentagon, and the fourth, United Flight 93, crashed in Pennsylvania after passengers attempted to retake control. Nearly 3,000 people were killed, making it the deadliest terrorist attack in history. The attacks reshaped U.S. foreign and domestic policy, leading to the War on Terror and wars in Afghanistan and Iraq.