1977: Tenerife Airport Disaster

KLM 747 PH-BUF, which would be destroyed in the Tenerife Airport Disaster on March 27, 1977. (Image via Wikimedia Commons)

On this date in 1977, 583 people died in the deadliest accident in aviation history.

Here are some things you may not have known about the Tenerife Airport Disaster.

KLM Flight 4805 from Amsterdam, and Pan Am Flight 1736 from Los Angeles via New York, were both traveling to Gran Canaria Airport at Las Palmas in the Canary Islands.

A bomb explosion at Gran Canaria Airport forced five large airliners, including the two 747s, to be diverted to the smaller Los Rodeos Airport on the island of Tenerife. As the airport was not equipped to handle so many large aircraft, the taxiway was blocked by parked jets, which forced the use of the runway as a taxiway. During the time the planes were parked, a dense fog had rolled in, greatly reducing visibility.

The passengers from the KLM flight were taken to the terminal while the plane was refueled. One passenger who lived on the island decided to go directly home and didn’t re-board the plane.

The airport on Gran Canaria reopened and the KLM flight was sent to the end of the runway to wait for clearance to takeoff. The Pan Am plane followed onto the runway after being told to take an earlier exit back onto the taxiway.

The fog was so thick that the controller in the tower couldn’t see the runway or the planes on it. The pilots couldn’t see each other either. The airport did not have ground radar at the time, so the only way to keep track of the planes was by voice on radio.

English is the international language of aviation. With a Dutch crew on the KLM flight, an American crew on the Pan-Am and Spanish controllers in the tower, chances for miscommunication were rife in the already difficult conditions. The KLM crew mistook the controller’s command to lineup for departure with clearance for takeoff and throttled up.

The Pan Am crew was still taxiing down the runway, having missed their intended and poorly marked taxiway.

While the KLM 747 was coming up to takeoff speed, the tower instructed the Pan Am crew to report when they were clear of the runway. The KLM flight engineer heard this and asked his captain if the Pan Am was clear. The KLM captain said “Oh, yes,” and continued with the takeoff.

The Pan Am crew suddenly saw the KLM landing lights approaching at takeoff speed, and turned hard left toward the grass to try to avert a collision. The KLM crew saw the Pan Am at about the same time and pulled up hard in an effort to climb over the Pan Am. This resulted in the KLM dragging its tail for 72 feet. The nose gear of the KLM cleared the Pan Am, but the engines, lower fuselage and the main landing gear tore through the Pan Am jet almost directly above the wing.

The KLM jet remained airborne momentarily, but stalled, rolled sharply and hit the ground about 500 feet past the collision. Its full load of fuel caught fire immediately.

Both planes were destroyed. All 234 passengers and 14 crew members on the KLM flight died, as did 326 passengers and nine crew members on the Pan Am jet. 54 passengers and seven crew from the Pan Am flight survived, including the the flight deck crew.

Investigators determined that the main cause of the collision was the KLM taking off without clearance. Other major factors included the weather and radio interference, while the use of non-standard language, the Pan Am jet missing the intended exit, and the overcrowding of the airport were contributing, but not critical factors.

As a result of the accident, several changes were made to international airline regulations. Flight crews are now required to read back instructions from the controllers, rather than just acknowledging them. The words “take off” are only used after clearance has been given, “departure” is used before clearance. Cockpit procedures were also changed to allow the flight deck crew to raise concerns in the event of a misunderstanding.

The Spanish government also installed ground radar at the airport after the collision.

The Pan Am 747 involved in the collision was historic in its own right. It took the first commercial flight by a 747 on January 22, 1970. It was also the first 747 to be hijacked, when a flight from New York to Puerto Rico was forced to land in Cuba.

Our question: What type of animal are the Canary Islands named after?

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Because we’ve recently featured 1977, we’ll spin the wheel to pick a year at random.

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Weekly question: When did Pan Am go out of business?

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