On September 11, 2001, United Airlines Flight 93 was hijacked by four terrorists as part of the coordinated attacks against the United States. While the aircraft was in flight, passengers and crew members were able to use onboard airphones and personal cellular devices to contact family members and authorities on the ground. Through these communications, the passengers learned that other hijacked planes had already been flown into the World Trade Center and the Pentagon.

Upon realizing that their flight was intended to be used as a weapon, the passengers and crew organized a collective effort to regain control of the cockpit. The ensuing struggle between the passengers and the hijackers resulted in the aircraft crashing into a rural field near Shanksville, Pennsylvania, at approximately 10:03 a.m. All 44 people on board, including the four hijackers, were killed. Investigations and historical accounts conclude that the passengers' actions prevented the hijackers from reaching their likely target, which officials believe was the U.S. Capitol building in Washington, D.C. The bravery of those on board is widely credited with saving countless lives on the ground by forcing the plane down before it could reach a populated government center.