On the afternoon of March 27, 1977, a thick fog settled over Los Rodeos Airport on the island of Tenerife. By the time it lifted, 583 people were dead — the victims of the worst aviation accident in history.
It began with a bomb. A terrorist attack at Gran Canaria Airport forced dozens of aircraft to divert to Los Rodeos, a smaller regional airport not designed for such traffic. Two of them were Boeing 747s: KLM Flight 4805 from Amsterdam, and Pan Am Flight 1736 from Los Angeles.
The airport quickly became congested. With no space at the gates, aircraft parked on the taxiway — which meant that when Gran Canaria eventually reopened, planes had to taxi down the main runway itself to reach the takeoff position.
"KLM 4805, you are cleared to the Papa beacon. Climb to and maintain flight level nine zero. Right turn after take-off. Proceed with ATC clearance."
KLM Captain Jacob van Zanten, one of the most experienced pilots in the airline's history, began his takeoff roll without receiving takeoff clearance. The crew believed they had been cleared. They had not.
At the same moment, Pan Am Flight 1736 was still on the runway, having missed its assigned exit in the fog. The two aircraft never saw each other until it was too late.
The KLM 747 struck the Pan Am jet at nearly full takeoff speed. The impact, fire, and subsequent explosions killed all 248 people aboard the KLM aircraft and 335 of the 396 on the Pan Am flight.
The Tenerife disaster fundamentally changed how aviation operates. Among the reforms introduced in the aftermath:
Standardized phraseology. The word "takeoff" was reserved exclusively for actual takeoff clearances. Phrases like "we're now at takeoff" — used by the KLM crew — were eliminated. Crews must now say "we are ready for departure."
Crew Resource Management (CRM). The investigation revealed that junior crew members hesitated to challenge the captain's decision. CRM training was introduced to encourage all crew to speak up, regardless of rank.
Ground radar. Los Rodeos had no ground radar, making it impossible for controllers to see where aircraft were in the fog. Ground radar became standard at major airports.
Jacob van Zanten had been so highly regarded at KLM that the airline used his photo in their advertising. His face appeared in in-flight magazines distributed on the very aircraft that would kill him.
Nearly half a century later, the lessons of Tenerife are still taught in every commercial pilot training program in the world. The disaster changed aviation permanently — and almost certainly saved hundreds of thousands of lives in the decades since.
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