Four planes were hijacked during the September 11, 2001 attacks, three of which were used to strike significant U.S. sites. American Airlines flight 11 and United Airlines flight 175 were flown into the World Trade Center’s north and south towers, respectively, and American Airlines flight 77 hit the Pentagon. United Airlines flight 93 crashed in a field near Shanksville, Pennsylvania, after passengers attempted to overpower the hijackers. The plane was believed to be headed to the U.S. Capitol building in Washington, D.C.