What Led To The Tenerife Boeing 747 Disaster 44 Years Ago?

Yesterday marked 44 years since the Tenerife airport disaster occurred. This accident was the most tragic in the history of aviation. However, how did this collision on March 27th, 1977 occur? Let’s take a look at the factors leading up to it.

What Led To The Tenerife Boeing 747 Disaster 44 Years Ago?
In March 1977, two Boeing 747 jets collided on the runway of Tenerife Los Rodeos Airport. Photo: Getty Images

External events

Both Boeing 747s involved in the accident were seeking to transport travelers going to the nearby island of Gran Canaria, where they were planning to spend their vacations. Pan Am Flight 1736 initially departed from Los Angeles International Airport (LAX) and was taking tourists to Gran Canaria for a 12-day Mediterranean cruise. The Boeing 747-121 (N736PA) ‘Clipper Victor’ made stops in Chicago (ORD) and New York (JFK) on the way.

13 flight attendants were taking care of the 380 guests on board the Pan Am service. Meanwhile, members of the flight deck crew were Captain Victor Grubbs, First Officer Robert Bragg, and Flight Engineer George Warns.

KLM Flight 4805 was a charter service for Holland International Travel Group and had arrived from Amsterdam Airport Schiphol. The Boeing 747-206B was full of tourists excited for a vacation in Gran Canaria.

Shortly before both jets were scheduled to arrive at Gran Canaria Airport (LPA) in Las Palmas, a terrorist group exploded a bomb at the site. Due to the subsequent injuries and panic, along with additional threats, Las Palmas was closed. Therefore, incoming aircraft, including this pair of jumbos, were diverted to Tenerife until Gran Canaria Airport was given the green light to open again.

A search for a supposed second device at Gran Canaria Airport took hours. Pan Am’s captain, Grubbs, decided to keep everyone on board his plane. Meanwhile, KLM’s captain, Jacob van Zanten was joined by 13 other crew members. He made the choice to let the 235 passengers disembark and have a stroll around Tenerife’s terminal until it was time to board again.

Pan Am Boeing 747-100
Pan Am introduced the Boeing 747 type at the beginning of the decade. Photo: Getty Images

Anxiety on the ground

Recordings highlight that the flight deck crew on the KLM 747 were concerned about strict government overtime rules and the repercussions of arriving back in Amsterdam late. Subsequently, not wanting to waste time getting permission to resume the trip, van Zanten chose to refuel his aircraft. During the refuel, Las Palmas had opened up. Nonetheless, the captain waited for the plane to fuel up.

With many of the other planes on the ground not as big as the 747, they could get around the sitting KLM unit to carry on their operations. However, Pan Am’s 747 was perched behind its fellow jumbo, and couldn’t make its way around it due to their sizes. Moreover, the KLM jet was now far heavier with the addition of fuel, so it would need more runway space to get into the air.

The weather conditions were fine until the moments before the accident. If it were not for KLM requesting extra fuel at the last minute, both 747s would have been taking off sooner. However, a heavy blanket of fog swept down from the hills, impacting visibility all of a sudden.

KLM 747 1973
KLM was also a fan of the jumbo. Photo: Getty Images

Odd positioning

The Telegraph shares that due to the congestion on the ground, the normal route to runway 30 was blocked. So, the departing planes were required to taxi down on the runway itself. When reaching the end, they made a 180-degree turn before taking off in the other direction. This process, which is rare at commercial airports, is called a “back track.”

Altogether, this move had put both 747s on the same runway at the same time. Notably, they were invisible not only to each other but also to the control tower. Additionally, the site didn’t have a ground tracking radar.

The KLM plane taxied ahead and onto the runway, with the Pan Am aircraft approaching several hundred yards behind. The KLM captain steered to the end before turning around and entering a hold position awaiting takeoff authorization. Pan Am’s instructions were to turn clear along a left-side taxiway to allow the other plane’s departure. Once safely off the runway, Pan Am would report so to the control team.

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A series of occurrences

Due to the fog, the Pan Am crew missed their assigned turnoff. Continuing to the next one isn’t usually a huge issue, but the plane was now on the runway for many more seconds. Meanwhile, having wheeled into position at the end, van Zanten came to a halt. His first officer, Klaas Meurs, took the radio and received route clearance.

Importantly, this was not a takeoff clearance, but instead, a process outlining turns, altitudes, and frequencies for use once in the air. This is standardly received well before a plane taking the runway. However, the crew members were too busy with checklists and taxi instructions up until this point. The pilots were also tired, frustrated, and anxious to get going. They also mistook the route clearance as authorization to takeoff and started moving the jet down the runway.

As the KLM plane was picking up speed, the Pan Am First Officer radioed ATC to inform them that they are still on the runway. The tower then called the KLM plane to ask them to wait for permission to depart. Normally, this would have prevented the KLM plane from taking off. However, because the tower and the aircraft were talking at the same time, the KLM crew did not hear the message.

All of a sudden, the Pan Am flight deck saw KLM 747’s lights emerge from the fog 2,000 feet away and approaching rapidly. Grubbs quickly tried to turn the plane off the runway. Meanwhile, van Zanten also soon saw the Pan Am plane. He couldn’t turn as it was too late, so he tried to get the aircraft airborne by pulling back on the elevators. Just as the KLM 747 began to gain height, its undercarriage hit the Pan Am plane’s midsection. This would cause a series of explosions amid the collision.

Tenerife Air Crash Getty
This accident rocked the industry. Photo: Getty Images

The aftermath

All of the KLM’s 234 passengers on the plane passed away (one passenger didn’t board again during the previous disembarkment), along with all of the crew members. There were also 335 fatalities on the Pan Am aircraft.

Pan Am purser Dorothy Kelly was just one of 61 survivors in the incident. She recalled how quickly everything occurred from the point of view in the cabin.

“I was standing at 1R, the forward right door, drinking a coffee Miguel (Torrech) had given to me and Carla (Johnson) was standing a few feet away. All of a sudden things were not right. Things were flying around the airplane and everything moved in slow motion. Nothing was like it had been moments before. I wasn’t in a position where I could see out of the plane and I thought a bomb may have exploded. Everything just changed in a moment,” Kelly said, as per a report shared by Confessions of a Trolley Dolly.

“The KLM airplane had peeled off the top of the Pan Am plane, just like peeling off the top of a sardine can, the top had rolled right off. Everyone in the section had gone…I remember people jumping. I looked over; it was like looking out of a second floor window about 25 feet down, and I was really scared because my feet were bare and you saw nothing but jagged metal down there and I said to myself ‘Oh, my God, we’ve survived this and we are going to kill ourselves jumping down on that stuff

Much needed measures were introduced to international regulations following this disaster. For instance, due to miscommunication and misunderstandings, there was soon a significant push to emphasize the use of a common language in aviation in the form of English. Moreover, there was a move to have more constructive responses to ATC instructions, rather than simple agreements to ensure that the receiver fully understands a message.

What are your thoughts about the Tenerife airport disaster? Let us know what you think about the factors in the comment section.