Date:	Sunday 27 March 1977
Time:	17:06
Type:	Boeing 747-206B
Owner/operator:	KLM Royal Dutch Airlines
Registration:	PH-BUF
MSN:	20400/157
Year of manufacture:	1971
Total airframe hrs:	21195 hours
Cycles:	5202 flights
Engine model:	Pratt & Whitney JT9D-7W
Fatalities:	Fatalities: 248 / Occupants: 248
Other fatalities:	335
Aircraft damage:	Destroyed, written off
Category:	Accident
Location:	Tenerife-Los Rodeos International Airport (TCI) -   Spain
Phase:	Take off
Nature:	Passenger - Non-Scheduled/charter/Air Taxi
Departure airport:	Tenerife-Los Rodeos International Airport (TCI/GCXO)
Destination airport:	Las Palmas-Airport de Gran Canaria (LPA/GCLP)
Investigating agency:	CIAIAC
Confidence Rating:	Accident investigation report completed and information captured

Narrative:
At 12:30 a bomb explodes in the Las Palmas passenger terminal. Because of warnings of a possible second bomb, the airport was closed. A large number of flights were diverted to Tenerife, a.o. KLM Flight 4805 from Amsterdam and PanAm Flight 1736 (coming from Los Angeles and New York).
Las Palmas Airport opened to traffic again at 15:00.
Because the PanAm passengers remained on aboard it was possible to leave Tenerife at once. The taxiways were congested by other aircraft however. This meant the PanAm crew had to backtrack on runway 12 for takeoff on runway 30. The entrance to runway 12 however, was blocked by the KLM Boeing. The PanAm flight had to wait for almost 2 hours before all KLM passengers (except 1) had reboarded and refueling had taken place.
The KLM flight was then cleared to backtrack runway 12 and make a 180deg. turn at the end. Three minutes later (at 17:02) Pan Am 1736 was cleared to follow the KLM aircraft and backtrack runway 12. The PanAm crew were told to leave the runway at the third taxiway and report leaving the runway. At 17:05:44
KLM 4805 reported ready for takeoff and was given instructions for a Papa beacon departure. The KLM crew repeated the instructions and added "We are now at takeoff". The brakes were released and KLM 4805 started the takeoff roll.
Tenerife tower, knowing that Pan Am 1736 was still taxiing down the runway replied "OK ...... Stand by for takeoff, I will call you." This message coincided with the PanAm crew's transmission "No ... uh we're still taxiing down the runway, the Clipper 1736". These communications caused a shrill noise in the KLM cockpit, lasting approx. 3.74 seconds.
Tenerife tower replied: "Papa Alpha 1736 report runway clear.", whereupon the PanAm crew replied: "OK, will report when we're clear". This caused some concerns with the KLM flight engineer asking the captain: "Is he not clear then?" After repeating his question the captain answers emphatically: "Oh, yes".
A number of second before impact the KLM crew saw the PanAm Boeing still taxiing down the runway. The crew tried to climb away and became airborne after a 65 feet tail drag in an excessive rotation.
The PanAm crew immediately turned the aircraft to the left and applied full power. The KLM aircraft was airborne, but the fuselage skidded over the PanAm's aft fuselage, destroying it and shearing off the tail. The KLM aircraft flew on and crashed out of control 150 m further on, sliding another 300 m bursting into flames.

PROBABLE CAUSE: "The KLM aircraft had taken off without take-off clearance, in the absolute conviction that this clearance had been obtained, which was the result of a misunderstanding between the tower and the KLM aircraft.
This misunderstanding had arisen from the mutual use of usual terminology which, however, gave rise to misinterpretation. In combination with a number of other coinciding circumstances, the premature take-off of the KLM aircraft resulted in a collision with the Pan Am aircraft, because the latter was still on the runway since it had missed the correct intersection."

Flight Safety Digest July 1995(1-10)/Flight Safety Foundation
ICAO Circular 153-AN/56 (p.22-68) Human factors report on the Tenerife accident / Air Line Pilots Association (ALPA)
'Tenerife report blames KLM', Flight International 23.12.78 (2240)
'Tenerife: the last analysis', Flight International 20.01.1979 (194-196)
Project-Tenerife.com

photo (c) ANP / C. Mulder; Tenerife-Norte Los Rodeos Airport (TFN); 29 March 1977; (CC:by-nc-nd)

photo (c) ANP / C. Mulder; Tenerife-Norte Los Rodeos Airport (TFN); 29 March 1977; (CC:by-nc-nd)

photo (c) ANP / C. Mulder; Tenerife-Norte Los Rodeos Airport (TFN); 29 March 1977; (CC:by-nc-nd)

photo (c) ANP / C. Mulder; Tenerife-Norte Los Rodeos Airport (TFN); 29 March 1977; (CC:by-nc-nd)

photo (c) ANP Foundation; Tenerife-Norte Los Rodeos Airport (TFN); 29 March 1977; (CC:by-nc-nd)

photo (c) Alfred Wittwer, coll. Werner Fischdick; Amsterdam-Schiphol Airport (AMS); May 1975

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