The Tenerife airport disaster in 1977 was a collision involving two Boeing 747 passenger aircraft on the runway of Los Rodeos Airport (now known as Tenerife North Airport) on the Spanish island of Tenerife, one of the Canary Islands. With 583 fatalities, the crash remains the deadliest accident in aviation history. All 248 aboard the fully fuelled KLM flight were killed. There were also 335 fatalities and 61 survivors from the Pan Am flight, which was struck along its spine by the KLM's landing gear, under-belly and four engines. Rescue crews were unaware for over 20 minutes that the Pan Am aircraft was also involved in the accident, due to the heavy fog and the separation of the crippled aircraft following the collision.
The collision took place on March 27, 1977, at 17:06:56 local time. The aircraft were operating as Pan Am Flight 1736 (the Clipper Victor) under the command of Captain Victor Grubbs, and KLM Flight 4805 (the Rijn) under the command of Captain Jacob Veldhuyzen van Zanten. Taking off in heavy fog on the airport's only runway, the KLM flight crashed into the top of the Pan Am aircraft backtaxiing in the opposite direction. The Pan Am had followed the backtaxiing of the KLM aircraft, under the direction of Air Traffic Control, and the KLM's flight crew had been aware of Pan Am backtaxiing behind them on the same runway. Despite lack of visual confirmation, due to the fog, the KLM captain thought that Pan Am had cleared the runway and so attempted to take off without further clearance to do so. Several other key factors contributed to the accident.