A Boeing 757 takes off from Washington Dulles International Airport en route to Los Angeles. In minutes, hijackers storm the cockpit and turn the plane back toward the nation's capital and straight into the Pentagon. A total of 189 people are dead, the fuselage has been vaporized, and investigators are under tremendous pressure to determine how this could have happened. Witness the crash of American Airlines Flight 77 and the ways in which the 9/11 attacks brought immediate and profound changes to commercial aviation throughout the world.