The Tenerife Airport Disaster, A Deadly Incident That Changed Aviation Forever

A virtual recreation of the collision between KLM Flight 4805 and Pan Am Flight 1736.

On March 27, 1977, unbeknownst to anyone, the deadliest incident in aviation history would end up happening, killing 583 people. Called the Tenerife Airport Disaster, it took place at the Los Rodeos Airport, which is now known as Tenerife North Airport, on the island of Tenerife in the Canary Islands of Spain. Two Boeing 747 aircraft, one operated by KLM Royal Dutch Airlines and the other by Pan American World Airways, slammed into each other on a narrow runway. To understand how this occurred, we need to take a look at what had happened earlier in the day.

Both planes were scheduled to land at Las Palmas Airport on a neighboring island. The KLM plane, KLM Flight 4805, had started in Amsterdam, Netherlands, and was carrying 235 passengers and 14 crew members, while the Pan Am plane, Pan Am Flight 1736, had started its journey in Los Angeles, with a stop in New York, and had 380 passengers and 16 crew members on board. Most of the passengers on the KLM flight were of Dutch origin, while Pan Am mostly had American passengers. Neither of the flights were scheduled for a stop at Tenerife, but a diversion had led them both here, setting the stage for disaster.

The Bomb Threat and Diversion

That morning, a bomb had exploded in a terminal at Gran Canaria Airport, and it had been planted by the Canary Islands Independence Movement. Eight people were injured, and officials suspected a second bomb. As a result, they closed Gran Canaria Airport temporarily and diverted all the flights that were going there to Los Rodeos Airport on Tenerife. Los Rodeos was small and only had one runway and one main taxiway. It was not equipped whatsoever to deal with planes as large as the Boeing 747. By the time the KLM and Pan Am flights got there, along with other diverted planes, the airfield was overcrowded. The Pan Am crew had asked to circle in the air until Gran Canaria reopened, since they had fuel. However, the air traffic control still told them to divert to Tenerife instead. This put two large planes at an airport unprepared to handle them, creating difficulties for both pilots and controllers.

Congestion and Delays

At Los Rodeos, the airport's limitations proved to be a problem. The single runway and sparse taxiways made it hard for planes to move around. The KLM plane blocked the Pan Am plane, which could not access the runway, since only 12 feet separated them. KLM captain Jacob Veldhuyzen van Zanten opted to fuel his plane at Tenerife to save time later since his flight had to return to Amsterdam, and the refueling, which took 35 minutes, delayed both planes. The Pan Am crew stood by, waiting to take off. Four passengers on the KLM plane also delayed the flight even further by not coming back to the aircraft promptly, though one lucky passenger, a woman from the area, chose not to reboard, leaving the plane with only 234 passengers. The crowded airport and delays annoyed everyone involved and put them on edge.

Weather and Communication Problems

While the aircraft stood by, thick fog, which Tenerife was infamous for, crept over the runway, reducing visibility to almost nothing. Pilots and controllers had poor visibility of the planes and runway, and the fog made it hard to get planes moving when Gran Canaria Airport reopened. Controllers had the Pan Am plane taxi down the runway and exit at a specific point so that the KLM plane could take off. The Pan Am crew struggled to locate the exit because of the fog and confusing instructions. The controllers all spoke English but used non-standard language. The KLM crew was also pressured by airline rules that limited the hours that pilots could work. Simply put, they wouldn’t be able to return to Amsterdam if they did not take off soon. The fog, the crowded airport, and the time pressure created a hazardous situation.

The Collision

As the Pan Am plane taxied down the runway, the KLM crew was preparing to take off. Captain van Zanten thought he was cleared for takeoff, but he had misheard the controller's message. The controller had read out route details, not takeoff clearance. The controllers were confused when the KLM crew replied with "we are now at takeoff." The Pan Am crew radioed that they were still on the runway, but their transmission coincided with another and caused static.

The KLM pilots never got the warning, and controllers did not know that the KLM plane was moving. KLM Flight 4805 accelerated down the runway towards the Pan Am plane. The Pan Am captain saw the lights of the KLM and tried to get off the runway. The KLM pilots also saw the Pan Am plane, and even though they tried to lift off early, it was already too late. The KLM plane crashed into the Pan Am aircraft, and a huge fireball erupted due to the extra fuel. All 248 people on board the KLM plane died, and 335 of the 396 on board the Pan Am plane died. There were 61 survivors from the Pan Am flight, but most were injured. The accident happened at 5:06 p.m.

Causes of the Disaster

Wreckage on the runway of Los Rodeos Airport after the incident.

The investigators identified several causes for the disaster. The main cause was the KLM captain's attempt to take off without clear clearance. The captain had plenty of experience, with over 11,700 hours, but he acted too fast. The fog meant planes could not be seen, and communications issues caused confusion. Overlapping radio messages blocked out the Pan Am warning, and vague phrases like "at takeoff" did not help. The crowded airport and time pressure caused everyone to hurry. In addition, the extra fuel on the KLM plane fueled the fire, lowering survival rates. All these factors combined caused the disaster, showing how small errors can add up to create a huge tragedy.

Aftermath and Aviation Changes

Investigators from the United States, Netherlands, and Spain reviewed what happened after the crash. They suggested changes to make flights safer. Standard words were provided to pilots and controllers to avoid misunderstandings. Crew Resource Management was instituted to enable all crew members to make comments when they had concerns. Airports were equipped with better equipment, like radar for bad weather. Pilots and controllers were also better trained, with special attention to clear communication and stress management. The Tenerife disaster showed the need for careful safety measures, and its lessons have enabled air travel to be safer today.