Apocalypse on the Runway: Revisiting the Tenerife Airport Disaster
Note: this accident was previously featured in episode 12 of the plane crash series on November 25th, 2017, prior to the series’ arrival on Medium. This article is written without reference to and supersedes the original.
It was an event which shook the world: on a windswept island in the Atlantic Ocean, two Boeing 747s collided on a fog-shrouded runway, claiming the lives of 583 people. The story of the world’s worst air disaster has since been told and retold countless times: by the handful of lucky survivors; by the firefighters who ran into the fog, not realizing the scale of the catastrophe; by the investigators who pieced together the cause; by journalists and authors compelled to tell the world what happened; and by sociologists and behavioral scientists seeking to understand why humans make mistakes. The accuracy and nuance of these retellings varies, but the thrust of each is the same, reflecting upon the banality of disaster, the unfairness of coincidence, and the randomness of fate. Yet the events of the 27th of March, 1977 occurred in an environment that made this outcome possible, a series of misguided human decisions which established the rules of the game well before the two 747s ever arrived in the Canary Islands. And so, as we launch into yet another account of the Tenerife Disaster, it is worth stepping back from the glaring carnage and the accusations of guilt to consider more important questions. Was anything learned? How can the loss of so many lives be rendered less senseless? More than forty years later, the uncertain answers to these questions still draw us back to that fateful day on Tenerife.
Far to the southwest of Portugal, in the glistening subtropical waters off the coast of Morocco, lie the Canary Islands. A string of seven volcanic summits rising from the Atlantic, the Canaries have been a part of metropolitan Spain since the fifteenth century. Ever since the advent of air travel, their towering mountains, sun-blessed beaches, and active volcanoes have made the Canary Islands one of Europe’s top tourist destinations, a favorite among off-season travelers looking for a slice of summer during less pleasant times of year.
In 1975, around two million tourists visited the Canaries, but at that time it could not have been said that the islands were a major travel hub. Travel infrastructure in the archipelago was more suited to the reality of the 1960s, when the number of tourists had been ten times less, and the system frequently broke down under the strain. Nevertheless, when aviation experts in the 1970s expressed their concern about the inevitability of a fatal collision between two jumbo jets, they expected it to occur in New York or London or Los Angeles — not at a tiny single-runway airport on an island off the coast of Africa, so far from what were traditionally considered the world’s busiest airways.
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Believe it or not, the 27th of March, 1977 began as a normal day. At around 45 minutes after midnight, Captain Victor Grubbs, First Officer Robert “Bob” Bragg, and Flight Engineer George Warns reported for duty at New York’s John F. Kennedy International Airport in order to fly a Pan American Airways tourist charter service to the Canary Islands. Their double decker Boeing 747–100 was filled with 380 passengers, many of them retired couples embarking on a package cruise, along with 16 crew. For the pilots, the journey would have been utterly routine; there had doubtlessly been many others like it during their long careers, which had allowed the three men to rack up a combined 47,000 flying hours. When the 747, nicknamed Clipper Victor, took to the skies that night, the passengers could not have been in better hands.
An hour later and an ocean away, at Schiphol Airport in Amsterdam, the crew of a KLM Royal Dutch Airlines Boeing 747–200 also reported for duty in advance of a flight to the Canary Islands. Captain Jacob Louis Veldhuyzen van Zanten was a living legend at KLM, the face of the airline’s advertising campaign and the head of its Boeing 747 training program. These days, he spent most of his time training new pilots, and the trip to the island of Gran Canaria would be his first regular line flight in twelve weeks. His First Officer, Klaas Meurs, was also no rookie, but he had only just upgraded to the 747, accumulating a mere 95 hours since acquiring his type rating, which Captain van Zanten had personally granted to him. Finally, Flight Engineer Willem Schreuder was the most experienced of them all, with over 17,000 hours in the air. He was also the president and co-founder of the European Flight Engineer’s Organization, a major international trade union. Alongside this prestigious crew, there were also 11 flight attendants and 235 passengers, most of them younger Dutch families heading to the Canaries for a few days of sun and surf, courtesy of tour operator Holland International.
The destination for both Pan Am flight 1736 and KLM flight 4805 was Gran Canaria Airport, located in the city of Las Palmas on the island of Gran Canaria. At the time this was the largest airport in the Canary Islands, and for tourists arriving from abroad it was the main port of entry. But, as it turned out, that also made it a target for those who were not satisfied with the way the islands were run.
Unlike most other North Atlantic archipelagoes, the Canary Islands were not uninhabited when Europeans and their armies first arrived in the 1400s. The islands have been home to the indigenous Guanches since the first millennium B.C., and even after 500 years of colonization some of their descendants have not forgotten the atrocities committed against their community. As the oppressive regime of dictator Francisco Franco began to unravel following his death in 1975, a pro-independence political party took advantage of the instability to launch an armed wing known as the Fuerzas Armadas Guanches, with the stated aim of winning self-government for the Canary Islands through terrorism. Although the group never directly killed anyone during its brief history, it would become most famous for setting in motion an unanticipated chain of events that went far beyond their modest terroristic ambitions.
Early on the afternoon of March 27th, the Fuerzas Aramadas Guanches detonated an improvised bomb inside a florist’s shop inside the terminal at Gran Canaria Airport, wounding the shopkeeper. As police hurried to respond to the attack, the airport received a phone call warning of a second bomb, prompting the authorities to shut down the airport and evacuate the terminal. Hundreds of people were rushed to safety as bomb detection squads moved in to scour the premises for further explosive devices.
Up in the air, the crews of the Pan Am and KLM 747s received the unwelcome news that their destination airport was closed until further notice. All traffic, they were told, would be diverted to the neighboring island of Tenerife. The Pan Am crew protested, explaining that they had enough fuel to hold over Gran Canaria for several hours, but without any clear timeline for reopening the airport, the controller could not grant their request. Everyone would have to land on Tenerife, then make their way to Gran Canaria once the coast was clear — without exception.
In 1977, the island of Tenerife was served only by a small, single-runway airport called Los Rodeos, situated on a saddle between two mountain peaks at a height of more than 2,000 feet (600 meters) above sea level. The airport was not unaccustomed to international traffic, but it usually served smaller jets operating for private low-cost and holiday-focused airlines from Europe, and generally in small numbers. It certainly was not built to accommodate Boeing 747s; it had no radar, no runway visibility measuring system, and no taxiway markings; and the centerline lights were out of service. To make matters worse, today was Sunday, and the control tower was short-staffed.
Within minutes of the bomb explosion on Gran Canaria, planes started to arrive at Los Rodeos in a never-ending stream. KLM flight 4805 was among the first to arrive, touching down at 13:38. In anticipation of further arrivals, the controllers instructed it to park down at the end of the main taxiway where it intersected runway 12. Expecting a long delay, the KLM crew allowed their 235 passengers to disembark into the terminal, where they were given special ID cards so they could be found again at the end of the layover. Meanwhile, more planes quickly piled up behind it, including Pan Am flight 1736, which arrived at 14:15. By half past 14:00, the number of planes had become so large that the queue spilled all the way across the parking apron and into parts of the main taxiway.
At 14:30, just 15 minutes after the arrival of the Pan Am 747 in Los Rodeos, bomb squads completed their sweep of Gran Canaria Airport. Finding no second bomb, the airport was promptly reopened. Upon receiving the good news, the Pan Am crew requested permission to start their engines and taxi to the runway for takeoff, as several smaller planes had already managed to do — only to be told by the controller that they probably wouldn’t fit past the KLM 747 still parked at the end of the taxiway. Furthermore, they couldn’t turn around and taxi in the other direction because there wasn’t enough room to pull a 180. Having been on duty all day, and with their passengers growing restless, the Pan Am pilots were itching to leave. First Officer Bob Bragg and Flight Engineer George Warns left the airplane to check whether they could fit past the KLM 747, only to return crestfallen: having paced out the distance between the KLM’s wing and the edge of the taxiway, they found it to be four meters too narrow.
As it turned out, the crew of the KLM 747 were in an even stickier situation. In 1974, the Netherlands had introduced a law which delineated strict new flight duty time limits, and allowed pilots to be held criminally liable for exceeding them. Possible penalties ranged from loss of license to outright imprisonment. Further compounding the situation, a 1976 law changed the way duty time limits were calculated, making the process so complex that pilots could only find out their limits by calling the company to ask. Understandably, the pilots of KLM flight 4805 were worried that they might not make it back to Amsterdam that night before their duty time expired, potentially incurring severe penalties. At Los Rodeos, a KLM dispatcher informed them that if they could leave Gran Canaria by 19:00, they should stay within limits, but that they should call again later to be sure. If they couldn’t make it, they would have to cancel the flight, and KLM would have to find enough empty hotel rooms to house all 235 passengers and 14 crew on a small island at the height of the tourist season.
Unfortunately, they would not be leaving Los Rodeos in a timely fashion. The process of rounding up all the KLM passengers proved to be extraordinarily difficult, ultimately running until 16:00, an hour and a half after Gran Canaria reopened. On board the Pan Am plane, agitation grew as flight attendants struggled to attend to the passengers, who had mostly embarked at Los Angeles the previous evening and had by now consumed every ounce of food and drink aboard the 747. Frustrated that they couldn’t depart until the KLM plane cleared the taxiway, the Pan Am crew expressed their displeasure with the KLM pilots, but were unable to do anything to expedite the process.
In the end, the KLM cabin crew never managed to corral all 235 passengers. Robina van Lanschot, a Dutch tour guide based on Tenerife, decided to go against protocol and made her way home from the airport without permission, a minor act of disobedience which would save her life. She could not have known that out of 249 passengers and crew who flew into Tenerife on flight 4805, she would be the only survivor.
Meanwhile, KLM Captain Jacob van Zanten made another calculated decision which would further delay their departure from Tenerife but might reduce their overall time on duty. Once all the passengers were on board, he decided to fill up with an additional 55,500 liters of fuel — enough to fly not just to Gran Canaria but all the way back to Amsterdam as well. Van Zanten expected to face long lines at the pump in Gran Canaria as diverted planes streamed back to the airport, potentially delaying their departure; therefore it made more sense to fuel up at Tenerife. Later reports would come to contradictory conclusions about whether this was necessary.
Throughout the afternoon, the weather at Los Rodeos continuously deteriorated. Tenerife rises directly into the path of oceanic winds blowing off the Atlantic, which results in unpredictable conditions on the upwind slope of the island. This problem becomes particularly acute on the saddle between the island’s two main mountain ranges, where the terrain funnels clouds directly over Los Rodeos Airport at a high rate of speed. By the time KLM flight 4805 began refueling sometime after 16:00, clouds were already streaking over the airport, creating intermittent conditions of low visibility. Both crews were acutely aware that if the visibility dropped below the minimums for takeoff, they would be stuck on Tenerife overnight.
Finally, at 16:51, KLM flight 4805 finished refueling and requested clearance to start its engines, and Pan Am flight 1736 followed suit 20 seconds later. After performing final checks and running up the engines, the KLM 747 taxied out onto runway 12.
Due to the prevailing wind out of the west, both planes would have to take off from runway 30 — the same runway, but in the other direction. This meant that they would have to taxi down to the far end of the runway before turning around, a process which was rapidly increasing in complexity due to shrinking visibility and the large number of planes still parked on the various taxiways. The controller was also struggling to figure out how best to handle the massive 747s. After some initial waffling over which route to use, he eventually instructed the KLM crew to “back-taxi” up the runway in the wrong direction, then make a 180-degree turn at the far end. Four minutes later, he cleared the Pan Am 747 to follow the KLM up the runway, then turn off at the third exit, the nearest one which was not blocked by parked airplanes. Captain Grubbs expressed his displeasure with taxiing on the runway before the KLM plane had taken off, but decided not to press the point with a controller whose grasp of English appeared to be shaky.
As both 747s crawled along the runway amid blowing fog, the controller and the two crews all lost sight of one another. With no ground radar at the airport, the controller had to rely on pilot reports to keep track of the locations of the 747s. But for the pilots, figuring out where they were and where they were going was easier said than done. Visibility oscillated between about 100 and 900 meters on a very rapid interval, and the taxiways were not marked with any sort of sign or painted number. And as if that wasn’t enough, the controller’s thick Spanish accent made it hard for the Pan Am crew to understand what he was saying. When the controller said “Leave the runway third one your left” [sic], the pilots spent the next two minutes trying to figure out whether he said “first” or “third.”
Meanwhile, the controller asked the KLM crew, “KLM four eight zero five, how many taxiways did you pass?”
“I think I just passed Charlie four now,” First Officer Meurs said, observing what appeared to be the fourth and final taxiway angling off to his left.
“Okay — at the end of the runway make one-eighty and report, ah, ready for ATC clearance,” said the controller.
Now, after several confusing exchanges, Pan Am First Officer Bragg finally asked, “Would you confirm that you want the Clipper one seven three six to turn left at the THIRD intersection?”
“The third one sir, one two three, third, third one,” the controller replied.
“That’s what we need, right?” said Captain Grubbs.
“Uno, dos, tres,” Flight Engineer Warns affirmed.
As the Pan Am crew ran through their taxi checklist, the KLM 747 arrived at the end of the runway and began its delicate 180-degree turn. Captain van Zanten had to give the maneuver his utmost concentration, because the 747 requires 42 meters to turn around, and the runway was only 46 meters wide.
The Pan Am crew, still taxiing down the runway, were struggling to find the third taxiway. According to their charts, the third exit was a narrow strip angling sharply back the way they came, requiring two successive 148-degree turns to get onto the main taxiway, which paralleled the runway. Later analysis would show that a Boeing 747 could not make the second turn because the taxiways were too narrow. The Pan Am crew instinctively knew this, but the controller, who was unfamiliar with the capabilities of the 747, did not.
“That’s two,” Captain Grubbs said, spotting the second exit drifting past them through the dense fog. For the next minute, the crew struggled to figure out which exit was in fact the third one.
“Yeah, that’s the forty-five there,” said Flight Engineer Warns.
“Yeah.”
“That’s this one right here.”
“Yeah I know.”
“Next one is almost a forty-five, but huh, yeah.”
“But it goes — yeah, but it goes ahead, I think it’s gonna put us on the taxiway.”
“Yeah, just a little bit, yeah.”
“Maybe he — maybe he counts these [as] three.”
Considering that a 747 could not negotiate the third taxiway, the crew considered whether the controller started counting up to three from the position they were in when the message was sent, by which time they had already passed the first one. That would mean they should leave the runway via the fourth and final exit, which was easy for a 747 to use. But nobody knew for sure.
“I like this,” someone drily commented. It did not take the power of hindsight to see that they were in a dangerous position.
On board KLM flight 4805, the crew finished the last takeoff checklist item, and First Officer Meurs called the checklist complete. Visibility at that point was 900 meters, but another wave of dense cloud could be seen headed toward them down the runway at a speed of about six meters per second. With a minimum takeoff visibility of 300 meters, they knew they needed to start rolling before the cloud enveloped them again.
At that moment, Captain van Zanten began to move the throttle levers forward, but First Officer Meurs said, “Wait a minute, we do not have an ATC clearance.”
Van Zanten pulled the throttles back to idle again. “No, I know that,” he said. “Go ahead, ask.”
ATC clearance, it must be said, is not the same thing as takeoff clearance. An ATC clearance is a description of the route which the plane will fly after departure, but does not give an aircraft permission to actually depart.
“The KLM four eight zero five is now ready for takeoff, and uh, we are waiting for our ATC clearance,” First Officer Meurs said over the radio.
“KLM four eight zero five, you are cleared to the Papa beacon, climb to and maintain flight level niner zero, right turn after takeoff, proceed with heading zero four zero until intercepting the three two five radial from Las Palmas VOR,” the controller replied.
First Officer Meurs started to read back the clearance. “Roger sir, we are cleared to the Papa beacon, flight level nine zero…”
At that moment, Captain van Zanten pushed the throttles to takeoff power and announced, “We’re going!”
Apparently taken by surprise, First Officer Meurs hastily finished his transmission: “…right turn out zero four zero until intercepting the three two five. We are now (at takeoff).”
Even after countless hours of post-facto analysis, no one would be able to say for sure whether Meurs said “at takeoff” or “eh, taking off.” But whatever he meant, one thing was clear: no one understood him to mean that KLM flight 4805 was already rolling. The controller thought he meant they were at the takeoff position, but he seemed to have a moment of doubt. He said “Okay,” then paused, as though trying to formulate a directive which would cover all contingencies. After two seconds, he continued, “Standby for takeoff, I will call you.”
At that exact moment, First Officer Bragg on the Pan Am, believing that the pause indicated the end of the transmission, keyed his mic and said, “And we’re still taxiing down the runway, the Clipper one seven three six.”
In what can only be considered a horrible coincidence, the simultaneous transmissions on the same frequency caused interference which manifested in the KLM cockpit as a loud squeal, partially drowning out the words underneath. If they had been paying close attention the pilots probably could have understood what was said, but such concentration is not normally needed and in this case was not applied. The only word the KLM pilots definitely heard was the controller’s “Okay,” which they mistakenly took for confirmation that the controller understood their intentions. Thus the controller’s instruction to wait for takeoff clearance, and the Pan Am First Officer’s position report, both passed unnoticed by precisely those people who most needed to hear them. And so KLM flight 4805 accelerated down the runway toward the dark wall of fog, unaware of the danger which lurked within.