The Tenerife disaster took place at 17:07 on March 27, 1977, when two Boeing 747s collided on the island of Tenerife, killing 583 people. The Tenerife disaster had the greatest number of casualties of any air disaster and remained the deadliest aircraft accident in history until the September 11, 2001 attacks. It is noteworthy that neither plane was in flight when the collision occurred.
On March 27, 1977 Pan Am Flight 1736, had taken off from New York's JFK International Airport, bound for the Canary Islands. The aircraft was a B-747-121, registration N736PA and named Clipper Victor. It happened to have been the first 747 to carry fare-paying passengers, on a flight from New York to London on 21 January 1970.
Upon approaching its final destination Las Palmas it was told the major airport was temporarily closed due to a terrorist bomb attack by Canary Island separatists, and was ordered to divert to Los Rodeos airport on the neighboring island of Tenerife, together with many other planes. The PanAm had landed at Tenerife and was waiting to go.
The KLM Flight 4805, PH-BUF, a B-747-206B flying as a charter full of vacationers, was getting ready to head back to Amsterdam via Las Palmas. PanAm could have taken off earlier, but the KLM plane needed to be fueled and blocked the PanAm jet's access to the runway. Once refueling was done, the KLM plane was to take off first, followed by the PanAm plane. Following the tower's instructions, the KLM jet taxied to the end of the main runway, made a 180 degree turn (difficult with a 747 on the narrow runway) and waited for ATC and takeoff clearance.
With KLM ready to go, PanAm was instructed to taxi along the same main runway until it reached exit 3, then to take the exit, get off the main runway and head to a parallel taxiway. Seemingly due to the heavy fog, they missed exit 3, which involved a sharp turn backwards and led straight back to the congested terminal area. They decided to go on till exit 4, which was heading in the right direction.
Tenerife Air traffic control gave the KLM plane clearance for the route it was to take after takeoff, but the KLM captain apparently mistook it to be permission for the takeoff itself. The co-pilot responded with a heavy Dutch accent with words that could either be "We are at take off" or "We are taking off". The control tower was confused with the message and asked for the KLM plane to stand by. However, simultaneous communication from PanAm made the response inaudible. Ironically, PanAm was reporting they have not finished taxiing. Both messages, if broadcast separately might give KLM time to abort the take off.
Due to the dense fog, the KLM's pilots were unable to see the PanAm 747 taxiing on the runway ahead of them. In addition, neither of the 747s could be seen from the control tower, and the airport was not equipped with runway radar.
Captain Jacob Veldhuyzen van Zanten, impatient because the flight had been delayed for hours and thinking that they had permission to take off, applied full power. While the KLM had started its take-off run, the concerned PanAm crew repeated that they were "still taxiing down the runway". On hearing this, the flight engineer expressed his concern about the PanAm not being clear of the runway, but it was overruled by the captain. The flight engineer apparently hesitated to further challenge van Zanten, possibly because he was not only senior in rank but also one of the most able and experienced pilots of the company.
As soon as the PanAm, still taxiing along, spotted the KLM 747's landing lights, the pilots tried to apply full power and take a sharp turn away from the runway, but the collision was only seconds away. The KLM plane, by now already partially free of the ground, slammed into the side of the PanAm plane, ripping apart the center of the fuselage of the PanAm jet (roughly what is directly above the wing.) The KLM plane rolled 180 degrees and slammed into the ground belly-up near the PanAm jet. All 234 passengers and 14 crew members in the KLM plane were killed, and 335 of the 396 aboard the PanAm flight (321 passengers and 14 crew members) perished. The PanAm captain was among the survivors (54 passengers and 7 crew members).
Later investigation showed that there had been misinterpretations and false convictions. Analysis of the CVR transcript shows that the KLM pilot was convinced that he had been cleared for take-off, while the Tenerife control tower was certain that the KLM 747 was stationary at the end of the runway and awaiting takeoff clearance. While there is debate about their relative importance, the general conclusion is that the disaster was caused partly by squelched radio messages (calls from both planes to the tower and vice versa canceled each other because they happened to be at precisely the same instant), partly by non-standard phrases used by the KLM co-pilot ("We're at take off") and the Tenerife control tower ("O.K."), and partly by the Dutch captain van Zanten seemingly being in a hurry to commence the delayed flight, possibly due to Dutch regulations on exceeding flight time (which later was hard to accept for the Dutch investigators, as the captain was otherwise known as a first class pilot).
Around 70 crash investigators from Spain, the Netherlands, the USA, and from the two airline companies were involved in the investigation. As a consequence of the accident, there were sweeping changes made to international airline regulations and to airplanes. It was made a worldwide rule that all control towers and pilot crews had to use English standard phrases. Airplane manufacturers began installing equipment that helped planes see through fog. Cockpit procedures were also changed. Hierarchical relations were played down. More emphasis was placed on decision-making by mutual agreement. This is known in the industry as crew resource management, and is now standard training in all major airlines.
Due to the frequent and dangerous fogs that cover the area around Los Rodeos airport in the North of the island, a second one was built in the South of the Island: the new Reina Sofía Airport, which serves the majority of Tenerife's domestic and international commercial flights; Los Rodeos, however, is still fully operational, mainly dedicated to cover regional flights within the Canary Islands.
- Report from Pan Am Accidents site (http://www.panamair.org/Accidents/Tenerife.htm)
- Coverage from Air Safety Network site (http://aviation-safety.net/backgrounder/19770327-0/index.shtml)