9/11
terrorist attacks that occurred in 2001, in which 19 militant Islamist men hijacked and crashed 4 commercial aircraft. Two planes hit the Twin Towers of the World Trade Center in New York City, causing them to collapse. One plane crashed into the Pentagon in Washington, D. C., and the fourth, overtaken by passengers, crashed into a field in rural Pennsylvania. Nearly 3,000 people were killed in the worst case of domestic terrorism in American history.