The document provides details about United Flight 93 which was hijacked as part of the September 11, 2001 terrorist attacks. It describes the hijackers, timeline of events including passenger phone calls revealing the hijacking, and passenger revolt that ultimately caused the plane to crash in a field in Shanksville, Pennsylvania, killing all 40 passengers and crew. It also outlines the design of the Flight 93 National Memorial built at the crash site to honor those who died.