On March 27, 1977, a KLM Boeing 747 passenger aircraft collided with a Pan Am Boeing 747 passenger aircraft on the runway at Los Rodeos Airport on Tenerife island.
The collision occurred when the KLM aircraft initiated a takeoff run in dense fog while the Pan Am aircraft was still on the runway.
The impact and resulting fire killed all 248 people on board the KLM aircraft and 335 of the 396 people on board the Pan Am aircraft. The 61 survivors were in the front section of the Pan Am aircraft. The accident, with a total of 583 fatalities, is the worst air disaster in aviation history.
KLM Flight 4805, operated by a Boeing 747-206B, originated at Amsterdam Schiphol Airport and carried 14 crew members and 234 passengers.
Pan Am Flight 1736, operated by a Boeing 747-121 aircraft, originated at Los Angeles International Airport with an intermediate stop at New York's JFK airport and carried 380 passengers and 16 crew members.
Both the Pan Am and KLM flights were destined for Gran Canaria Airport (GCA) on the tourist island of Gran Canaria, one of the Canary Islands.
As both flights approached the GCA, a bomb planted by the separatist Canary Islands Independence Movement exploded in the GCA terminal injuring eight people.
After the initial explosion, a threat of a second bomb caused authorities to close the airport. All inbound flights to GCA were diverted to Los Rodeos Airport.
[caption id="attachment_1105456" align="alignnone" width="800"] A graphic showing the Tenerife Airport, the red star indicates the point of collision. - Graphic courtesy Ramesh Lutchmedial[/caption]
Los Rodeos airport, with only one runway and one long parallel taxiway, had to accommodate all aircraft diverted by the terrorist incident requiring parking on the long taxiway, making it unusable for taxing. Consequently, departing aircraft had to backtrack along the runway to the takeoff position.
After the bomb threat was contained, GCA was reopened. The Pan Am aircraft was ready to depart Tenerife for GCA.
However, access to the runway was obstructed by the refuelling of the KLM aircraft as the KLM captain decided to fully refuel at Los Rodeos Airport to save time.
After the KLM aircraft was ready for departure, the tower instructed the KLM aircraft to backtrack along the runway and then make a 180-degree turn to get into takeoff position.
Air Traffic Control (ATC) then instructed Pan Am to follow KLM down the same runway and turn off at the third exit and use the parallel taxiway.
There were no markings or signs to identify the runway exits. With poor visibility, the Pan Am crew identified the unmarked exits using an airport diagram and mistakenly ended up at exit C-4
The KLM aircraft completed its 180-degree turn and after lining up on Runway 30, the KLM captain advanced the throttles and the aircraft began to move forward.
The co-pilot advised him that ATC clearance had not yet been given and the captain responded: "I know that. Go ahead, ask."
The co-pilot then radioed ATC that they were "ready for takeoff"
