The Tenerife airport disaster was a fatal collision between two Boeing 747 passenger aircraft which occurred on Sunday, March 27, 1977, 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 a total of 583 fatalities, the crash is the deadliest accident in aviation history.
After a bomb exploded at Gran Canaria Airport, many aircraft were diverted to Tenerife. Among them were KLM Flight 4805 and Pan Am Flight 1736 – the two aircraft involved in the accident. The threat of a second bomb forced the authorities to close the airport while a search was conducted, resulting in many airplanes being diverted to the smaller Tenerife airport where air traffic controllers were forced to park many of the airplanes on the taxiway, thereby blocking it. Further complicating the situation, while authorities waited to reopen Gran Canaria, a dense fog developed at Tenerife, greatly reducing visibility.
When Gran Canaria reopened, the parked aircraft blocking the taxiway at Tenerife required both of the 747s to taxi on the only runway in order to get in position for takeoff. The fog was so thick that neither aircraft could see the other, nor could the controller in the tower see the runway or the two 747s on it. As the airport did not have ground radar, the only means for the controller to identify the location of each airplane was via voice reports over the radio. As a result of several misunderstandings in the ensuing communication, the KLM flight attempted to take off while the Pan Am flight was still on the runway. The resulting collision destroyed both aircraft, killing all 248 aboard the KLM flight and 335 of 396 aboard the Pan Am flight. Sixty-one people aboard the Pan Am flight, including the pilots and flight engineer, survived the disaster.
As the accident occurred in Spanish territory, that nation was responsible for investigating the accident. Investigators from the Netherlands and the United States also participated. The investigation revealed that the primary cause of the accident was the captain of the KLM flight taking off without clearance from Air Traffic Control (ATC). The investigation specified that the captain did not intentionally take off without clearance; rather he fully believed he had clearance to take off due to misunderstandings between his flight crew and ATC. Dutch investigators placed a greater emphasis on this than their American and Spanish counterparts, but ultimately KLM admitted their crew was responsible for the accident, and the airline financially compensated the victims’ relatives.
The accident had a lasting influence on the industry, particularly in the area of communication. An increased emphasis was placed on using standardized phraseology in ATC communication by both controllers and pilots alike, thereby reducing the chance for misunderstandings. As part of these changes, the word “takeoff” was removed from general usage, and is only spoken by ATC when actually clearing an aircraft to take off. Less experienced flight crew members were encouraged to challenge their captains when they believed something was not correct, and captains were instructed to listen to their crew and evaluate all decisions in light of crew concerns. This concept was later expanded into what is known today as Crew Resource Management. CRM training is now mandatory for all airline pilots.