The Tenerife airport disaster of 1977 involved a collision between a KLM Boeing 747 and a Pan Am Boeing 747 on a runway at Los Rodeos Airport (now Tenerife North Airport) in Tenerife, Canary Islands, Spain. The collision killed 583 people and remains the deadliest accident in aviation history. Both planes were diverted to Los Rodeos Airport from Gran Canaria Airport due to a terrorist incident. The investigation concluded that the primary cause was the KLM captain taking off without clearance in dense fog, under the mistaken belief that clearance had been given. Communication failures between air traffic control and the pilots contributed to the disaster.