KLM 4805 and Pan Am 1736: The Two Boeing 747s That Collided Almost 50 Years Ago

The deadliest air crash in aviation history occurred on March 27, 1977, when two fully loaded Boeing 747s collided on a runway at Los Rodeos Airport in Tenerife, killing 583 people.

A KLM 747 began its takeoff run while a Pan Am 747 was still taxiing on the same runway. Pilot error and departure without clearance were the primary causes, but several other factors contributed.

583 Lives Lost: The Chain of Errors Behind the Tenerife Disaster

Both aircraft had been diverted from Gran Canaria Las Palmas Airport after a terrorist bomb exploded in its terminal, with a warning of a second device. Tiny Los Rodeos, with one runway, a parallel taxiway and limited parking, was overwhelmed.

Diverted jets filled the taxiway, forcing departing aircraft to taxi along the runway, and only two air traffic controllers were on duty.

Fog made matters worse. Drifting cloud cut visibility for the Pan Am crew to under 100 metres, and the tower could not see the runway end. KLM’s decision to fully refuel delayed departure further.

The Pan Am jet missed the instructed third exit and continued towards the fourth. At 17:06, KLM’s crew gave a read-back ending “we are now at takeoff” without clearance.

Radio interference blocked the tower’s “stand by” and Pan Am’s position report. The KLM flight engineer twice asked whether Pan Am was clear, but the question went unheeded.