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What REALLY Caused the Tenerife Airport Disaster?! The WORST Aviation Accident in History

(somber music) – [Petter] Two fully loaded Boeing 747s are taxiing through the thick fog on the runway preparing for takeoff. In a few moments, something will happen that will shock the world. How was this possible? Stay tuned. – Actually, I'm in a– – 100, 50, 40, 30, 20, 10. – A huge thank you to Curiosity Stream for sponsoring this video. The story about the Tenerife airport disaster is filled with frankly incredible coincidences. Let's see in the end of this video, if you can list all of the things that if they would have just happened slightly differently, this disaster could have been avoided. The chain of events start on the 26th of March, 1977 when Pan Am Flight 1736, which is a Boeing 747-100 with call sign Clipper 1736 takes off from Los Angeles International Airport with original destination New York to pick up some passengers and then fly down to Las Palmas in the Canary Islands.

This flight is chartered by Royal Cruise Lines and because it's a shorter flight, it's completely fully booked on its last leg. And it's mostly elderly passengers who are due to get onto a cruise ship when they reach Las Palmas. Las Palmas is the capital of the Canary Islands and is situated on Gran Canaria, which is one of the eight main islands of the island group. The Canary Islands is situated about 100 kilometers west of the Moroccan coastline, making it the most southern part of the Spanish territory. And because of its tropical and subtropical climate, it's a real hotspot for tourists from mainly Europe but all over the world.

Now the Canary Islands, back in 1977 had a little bit of political friction going on. A group called the MPAIAC was fighting for independence of the Canary Islands from Spain, or at least to get a little bit of recognition and attention by the central government. And it did so using both non-violent and violent political campaigns. And one of those campaigns is going to form the first piece of the puzzle, leading up to this disaster. In command of Pan Am Flight 1736 was 56-year-old Captain Victor Grubbs. Assisting him was 38-year-old First Officer Robert Bragg and 46-year-old Flight Engineer George Warns. They were a very, very experienced flight crew and they took over the flight in New York for the final leg down towards Las Palmas. When the aircraft arrived in New York, it was actually about 45 minutes delayed, which meant that the outbound flight down towards Las Palmas also became slightly delayed. At time 07:42, Clipper 1736 took off from JFK International Airport in New York and started flying down over the Atlantic Ocean towards Las Palmas. On board, there were a total of 16 crew members and 380 passengers.

While the Pan Am aircraft was making its way down over the Atlantic, another Boeing 747, a KLM Flight 4805 was getting ready to depart from Amsterdam down towards Las Palmas Airport. This was also a shorter flight chartered by Holland International Travel Group and they were due to take their passengers from Amsterdam, bring them down to Las Palmas, and then make a turnaround down there, refill the aircraft, get new passengers on and then fly back to Amsterdam as KLM Flight 4806, making it a fairly long day for the involved crew.

In charge of these two flights was Captain Jacob Veldhuyzen van Zanten, is 50 years old at the time, and he was working as the Chief Flight Instructor on the Boeing 747 fleet for KLM. This meant that he spent quite a lot of his operating hours in the simulator, instructing other pilots and maybe not as much time in the actual aircraft. One of the pilots that had been trained on the type by Captain Jacob van Zanten and indeed had been checked out by him just a few months earlier, was First Officer Klaas Meurs who's gonna be flying together with Van Zanten this afternoon.

Together with them, was also Flight Engineer Willem Schreuder. Willem Schreuder was very experienced and he was also known to not be afraid to speak his mind, something that we'll see soon enough. At nine o'clock sharp on the 27th of March, 1977, KLM flight 4805 took off from Schiphol Amsterdam International Airport with 14 crew members and 234 passengers on board and started its travel down towards Las Palmas. As these two aircraft was now making their way down towards their destination, two young men walked into the terminal building in Las Palmas Airport. They walked up to the flower shop that was close to the check-in desks. And they stood there for a while before they turned around and hurriedly went outside of the terminal building. Behind, they left a bag and what no one noticed at the time was that the bag was ticking. (timer ticking) At exactly one o'clock in the afternoon, a desk clerk inside of Las Palmas Airport received a phone call from someone claiming that they were a representative of the MPAIAC, saying that there were bombs put inside of the terminal building, and they had exactly 15 minutes to clear the entire building out.

Almost to the second, 15 minutes later, the bomb that was placed inside of the bag, next to the flower shop exploded. This caused part of the roof inside of the terminal building to fall down and other widespread damage, as well as injuring four people inside of the building. But remember how the person who called said that there were bombs, as in plural? Well, now the authorities needed to assume that there was more than one bomb inside of the building, so they needed to search it. And because of that, a decision was taken to stop all inbound flights into Las Palmas Airport. Almost exactly at the same time as this was happening down on the ground, KLM flight 4805 arrived into holding pattern above Las Palmas. Initially, they were told to hold, to wait, but pretty soon, they were told that we don't know how long this holding is going to take or how long the cleanup is going to take.

So you need to divert towards Los Rodeos Airport in Tenerife. This meant a short 25-minute flight over towards Los Rodeos, and at time 13:38, KLM 747 touched down on Runway 30 in Los Rodeos Airport. They taxied up until almost the terminal building as far north as they could on the apron, and they parked there. As the KLM flight was diverting, Pan Am Flight 1736 had also entered a holding pattern a few thousand feet above the KLM aircraft. They heard the news about the bomb just like the KLM flight did. And they also asked if they, potentially, could hold instead of diverting because they were also holding a lot of extra fuel on board. But just like the KLM flight, the Pan Am Flight was also told that no, we will not have any aircraft in our airspace, so please divert over towards Los Rodeos Airport so they did and they landed at time 14:15, about 37 minutes after the KLM flight and also taxied to the apron.

And at this point, Los Rodeos Airport had started to fill up with all of the inbound flights that were supposed to come in to Las Palmas, was now being diverted, which meant that both the apron and the taxiways was now becoming quite crowded with diverted flights. Now let's talk a little bit about the airport that these two aircrafts have just diverted to. Los Rodeos Airport is situated up in the northeastern corner of Tenerife. It's situated on a hill at an altitude of about 2,000 feet. Now Tenerife is dominated by the biggest mountain in Spain, actually, which is a volcano called Pico del Teide.

And Pico del Teide creates some quite unique metrological phenomenon where these humid trade winds that are coming in from the Atlantic is getting pushed up against the mountain side. And when it does so, it cools down, the moisture falls out and start forming clouds or fog. And that can happen really, really quickly. This also means that down on the southern side of Tenerife, it's almost always sunny. So the kind of weather that you associate with going to the Canary Islands is down south. But up in the north, it's almost always humid. There's a lot of rain, it's a lot greener, there's lot of vegetation there. And because the airport is situated at 2,000 feet altitude, it means that even reasonably high clouds, so 2,000 feet high clouds, when they come in over the airport, they touch ground.

And this causes a very interesting phenomenon where it's not quite fog, because when you think of fog, you think of something where the visibility stays more or less the same over time, maybe it's 500 meters visibility and it stays the same. But because what you have here is actually sometimes rolling clouds that are coming in and disappearing, you can have really big variations in visibility where it is maybe two three kilometers visibility in one minute and three minutes later, it's down to 300 meters.

When these two aircraft arrived into Tenerife, the visibility was good. It was a good day but that, very quickly, started changing. And that's what we'll come into in a minute. Another thing about Las Rodeos Airport is that it had a very poor safety record. Between the years of 1965 and 1968, there was, on average, one crash per year in the airport or in the surroundings, claiming 98 lives. And just a few years before this disaster, there had been another serious accident happen. Because of this, a decision had been taken to build a new airport down in the southern part of Tenerife instead where the weather was much better.

This airport was actually paved and almost ready to take into use in 1977 but because of some political infighting, that hadn't happened yet. This new airport down south actually had ground radar but Tenerife North, Los Rodeos Airport, did not have ground radar at the time of the accident. When the KLM flight pulled up and parked next to the terminal building, initially Captain Van Zanten and his crew wanted all of the passengers to stay on board. I'm guessing he probably was hoping that this was just gonna be a very short ground delay and that they could depart towards Las Palmas almost immediately. But after about 20 minutes, it became clear that this was not gonna be the case, and he decided that the passengers could disembark, go into the terminal building, stretch their legs a little bit, maybe grab something at the bar, and he issued them with reboarding passes so that they quickly could get back onto the aircraft if they were told that Las Palmas had opened again.

The Pan Am aircraft that came in a little bit later, wanted to do the same thing but were told that the terminal building was now completely full with all of the KLM passengers and that it wouldn't be good to mix the two. So the Pan Am crew decided to keep everyone on board, but they did ask for steps to be brought up towards the aircraft so that the passengers could go up onto the steps, stretch their legs a little bit, get some fresh air while they were waiting. The KLM passengers stayed inside of the terminal building for about two hours before they were reboarded. In the Pan Am cockpit, the crew tried to make the best out of the situation. Captain Grubbs made a PA telling all of the passengers that those who wanted could come in and visit the flight deck and he was guiding them around, showing this marvelous aircraft, this is the Boeing 747, to them. And the spirit was quite good even though they had been working for a long time at this point. In the KLM cockpit though, the mood was very different because Captain Van Zanten and his first officer and flight engineer has started talking about the recent changes in Dutch flight time limitation legislation.

Up until recently, before 1977, there had been quite lax rules regarding how long a pilot could work, but recently, those rules had changed dramatically. And there was now a very clear limits to how long you were allowed to operate. And if you as a captain went outside of these limitations, you would face a judge and potentially serve jail time. And this is what they were discussing because they could clearly see that if the ground delay would become much longer, well, then they would have to go very quickly over towards Las Palmas, have minimum delay there in order to be able to return to Amsterdam, and land within these limitations.

This made the flight crew quite anxious. They did not want to get stuck on Las Palmas. Captain Van Zanten had his wife at home and his two children. He said specifically, that he was afraid that his wife was gonna hear the news about the bomb in Las Palmas and become very, very worried if she knew that he was down there and was overnighting there. So they were really looking into ways that they could minimize the delay as much as possible to get themselves back towards Amsterdam. And this is where Captain Van Zanten takes a decision that's gonna have very dire consequences because he decides that if he's gonna be sitting on the ground here, he might as well be uploading as much fuel as he need to fly over to Las Palmas and to fly back to Amsterdam.

That way, he's gonna minimise the time on the ground in Las Palmas. This is a very sound decision. This is something I completely understand myself because if you're stuck there, why not utilize the time to upload the fuel? But once you start a fueling of a 747, it's a fairly big operation, it's not something that you want to stop. So he was kind of gambling that this delay was going to take another hour or so for them to be able to complete their fueling process and, crucially, this fueling process was also going to make his jet about 15% more heavy.

That would mean that he would need a higher speed in order to take off later on and also a longer takeoff distance. Only minutes after Captain Van Zanten has initiated refueling of his jet, he gets notice that Las Palmas has now opened again that they could go and fly over. Weather is still good, but now lower clouds starting to roll in from the hills and the visibility is getting worse minute by minute. Captain Grubbs in the Pan Am flight has heard the same message and he asks for start up but he is told that, unfortunately, now the KLM flight is fueling and there is not enough ground clearance for him to be able to maneuver his jet up and past the KLM flight in order to enter the runway and backtrack for departure. He is going to have to wait for the KLM flight to finish refueling for them to depart before he is allowed to taxi out and take off. When Captain Grubbs heard this, he went out onto the radio frequency and he said, "How long is this fueling going to take?" And Captain Van Zanten responded from the KLM cockpit saying that, "It's gonna take another 20 minutes to half an hour." Captain Grubbs in the Pan Am cockpit was not happy with this.

Instead, he sent out his flight engineer and his first officer to physically measure whether or not they could squeeze by the KLM jet on the apron. But when they came back in, they confirmed that the distance was not big enough, it was less than 20 feet short, but it was short, so they would have to sit and wait until the KLM had finished refueling. At the same time, all of the passengers and crew had returned back to the KLM aircraft and were now getting ready for departure, all except one. Mrs. Robina Monique van Lanschot was a worker for the company that had chartered the flight in the first place. And she had her boyfriend actually living on Tenerife so she had, during the ground time, checked if she could possibly stay there, together with him instead of taking the flight back towards Las Palmas. And that was granted. So at the time all of the other passengers were boarding the flight, she was already in the car, getting away from the airport, together with her boyfriend. And that is going to turn her into a very rare statistic. At time 16:45, the KLM aircraft had finished refueling.

And the last pieces of paperwork were delivered to the cockpit. Captain Van Zanten and his crew was now trying to complete the before-start checklist, and you can hear on the cockpit voice recorder how Captain Van Zanten is actually trying to slow things down. And he was saying things like, "Hey, give the man a chance," indicating that the first officer was working on his Scan Flow at the same time as the checklist was being read. But even though he was trying to moderate the pace, he was then heard just a few minutes later, before the checklist had been completed, calling for startup clearance and this is something that's normally done by the first officer.

So the fact that Captain Van Zanten was doing this himself indicate that he was also indeed trying to speed things up. Now before we go into the accident sequence of this video, I just wanna share a few words from my sponsor who's helping me make this kind of content possible. Now I know that you guys are watching my videos because you love learning new things and finding out the nitty-gritty, nerdy details behind each story. And if that's true, you should seriously check out the sponsor of this episode, which is Curiosity Stream. Curiosity Stream is a high quality subscription streaming service with thousands of great nonfictional stories and documentaries from some of the best filmmakers in the world.

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Now back to the video. At time 16:56, the KLM crew had finished starting up their engines and they now were ready to taxi. They went on to the ground controller frequency and were cleared to taxi into holding position for Runway 12. When they approached the holding position, they got transferred over to the approach controller and the approach controller cleared them to enter Runway 12, backtrack and then turn off the runway on the third exit on their left-hand side. The first officer read this back but instead of reading back the third exit, he read back the first exit which is kind of easy to understand because third and first can sound very similar, especially on radio frequency. When the approach controller heard his misunderstanding, he changed his mind and he changed the clearance to just backtrack all the way Runway 12 until you reach the end of the runway, make 180-degree turn and then hold position.

This was read back by the first officer but only a few seconds later Captain Van Zanten, came onto the same frequency and asked whether or not he should turn left onto charlie one which is, once again, the first exit on the left-hand side. The approach controller said, "No, continue, taxi straight ahead." And he said fine, he continued taxiing down. But when they passed taxiway charlie four, which is the fourth exit on the left-hand side, Van Zanten, again, turned over in the cockpit to his first officer and asked whether he should turn off there. This can maybe be interpreted as a little bit of confusion in the KLM cockpit at this time.

But with my experience, when you're taxiing in low visibility conditions, it's very, very hard actually, you see very little. It's actually a quite scary situation where you only see a few lights. And in this case, the centerline lights of the runway wasn't working either. So it's quite common that you, as a captain, keep asking your first officers to confirm the taxi route and confirm which turn it is. Whether you have the slightest little doubt about where you are or what you should do, you always ask so I didn't find that very strange, but it is also possible that Captain Van Zanten is now starting to think ahead and he's starting to think about the flight over to Las Palmas, the potential of delays in Las Palmas, and then the flight back towards Amsterdam and the flight time limitations, and he could start to become a bit distracted. And if that's the case, well then that could indicate that he's actually losing a little bit of current situational awareness because he is thinking ahead, something that we captains also tend to do, especially when there's trouble brewing.

And that could explain the actions that he's about to take next. As the KLM aircraft is taxiing now, the visibility was indicated to be around 500 meters, which is quite bad visibility. But some witnesses at the airport estimated that it could be at times as low as 100 meters, because they were now in that type of situation that we were talking about before, where there was low clouds that was moving over the runway. And this meant that at times, the visibility was really poor. And then one of these clouds could move out of the way and the visibility could improve quite significantly. And this was also indicated because the cockpit voice recorder indicates that the windshield wipers in the KLM cockpit was on for a couple of minutes.

But as the aircraft was reaching the end of the runway and started to turn around, they actually turned off the windshield wiper, indicating that the visibility, possibly, was a little bit better at that part of the runway. At the same time as the KLM aircraft is now backtracking runway, Clipper 1736, the Pan Am 747, receives their startup clearance. They start up all of their four engines and they request taxi clearance. And as they're now taxiing out towards the same holding position for Runway 12, Captain Grubbs is indicating to his fellow flight crew members that he would actually like to stay off the runway to wait until the KLM flight has departed instead of backtracking behind them. Unfortunately, this is never really transmitted on to air traffic control because as he is talking about this, they get several radio calls and also a frequency change. And when they change over to the approach frequency, which is the same frequency as the KLM aircraft is on, the approach controller gives them the clearance to enter Runway 12, backtrack and then turn the third exit towards the left of the runway, which is the same clearance as they originally gave to the KLM aircraft.

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