D. B. Cooper was an unidentified man who hijacked Northwest Orient Airlines Flight 305, a Boeing 727 aircraft, in United States airspace on November 24, 1971. During the flight from Portland, Oregon, to Seattle, Washington, the hijacker told a flight attendant he was armed with a bomb, demanded $200,000 in ransom, and requested four parachutes upon landing in Seattle. After releasing the passengers in Seattle, the hijacker instructed the flight crew to refuel the aircraft and begin a second flight to Mexico City, with a refueling stop in Reno, Nevada. About 30 minutes after taking off from Seattle, the hijacker opened the aircraft's aft door, deployed the staircase, and parachuted into the night over southwestern Washington. The hijacker has never been found or conclusively identified.

Aircraft hijacking is the unlawful seizure of an aircraft by an individual or a group. Dating from the earliest of hijackings, most cases involve the pilot being forced to fly according to the hijacker's demands. There have also been incidents where the hijackers have overpowered the flight crew, made unauthorized entry into the cockpit and flown them into buildings – most notably in the September 11 attacks – and in several cases, planes have been hijacked by the official pilot or co-pilot; e.g., Ethiopian Airlines Flight 702.