Widerøe Flight 933

Widerøe Flight 933, also known as the Mehamn Accident (Norwegian: Mehamn-ulykken), was the crash of a de Havilland Canada DHC-6 Twin Otter operated by Norwegian airline Widerøe. The Twin Otter crashed into the Barents Sea off Gamvik, Norway on 11 March 1982 at 13:27, killing all 15 people on board. The results of the four official investigations were that the accident was caused by structural failure of the vertical stabilizer during clear-air turbulence. A mechanical fault in the elevator control system caused the pilots to lose control of pitch; and either a series of stalls or a high-speed gust of wind caused the aircraft to lose altitude without the ability of the crew to counteract, resulting in the failure of the vertical stabilizer.

The accident occurred during a NATO military exercise, within a self-declared no-fly zone for allied military aircraft. An extensive search and rescue operation was carried out and the submerged wreck was found on 13 March. The aircraft and all but one of the deceased were retrieved. An official investigation was concluded on 20 July 1984.

A conspiracy theory later emerged after the accident investigation was concluded, claiming that the accident was caused by a mid-air collision with a Harrier jump jet of the British Royal Air Force. The theory is based on reports which emerged years or decades after the accident. The claims and renewed press interest resulted in three additional investigations, established in 1987, 1997, and 2002. All four investigations came to the same general conclusions and rejected a collision.