On Tuesday morning, September 11, 2001, the United States came under attack when four commercial airliners were hijacked in an act of terrorism. Two planes were flown into the World Trade Center in New York and a third into the Pentagon in Virginia. Nearly 3,000 people tragically lost their lives. Thanks to the heroic actions of the 40 passengers and crew aboard the fourth plane -- Flight 93 -- the U.S. Capitol was saved.