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How to Explain the Disaster at Tenerife

On March 27, 1977 the deadliest disaster in aviation history took place on the Spanish island of Tenerife. In the midst of take off, going approximately 160 mph, KLM flight 4805 collided with Pan Am flight 1739 half way down the runway, killing 583 people. The KLM captain was Jacob Van Zanten, KLM’s chief flight instructor who had just returned from a six month safety course for commercial pilots. The subsequent investigation concluded that Van Zanten took off without clearance, thereby causing the crash. How could such a credited and experienced pilot make such a catastrophic mistake?

The events that preceded the accident were a recipe for disaster. A terrorist bomb had exploded at Gran Canaria International Airport, forcing several planes to divert to Tenerife, a small airport not used to handling large commercial jets. The control tower was understaffed, their English was weak, and a heavy fog had set it that prevented Van Zanten and his crew from seeing no more than 300 meters. All of these inputs contributed to Van Zanten making the fateful decision to takeoff without permission from the control tower.

The accident was also very preventable. Van Zanten could have doubled checked with the control tower or waited for the fog to lift. However, his emotions got the best of him and his lack of patience cost him his life, and the lives of others. An expert with years of experience makes a rookie mistake and turns out to be flat-out wrong. Why?

It turns out that there are a lot of answers to this question (mistakes and errors, especially those having to do with the aviation business, are hot topics in the popular psychologist literature), and I have seen the Tenerife disaster comes up in three books: The Invisible Gorilla (p. 20), Being Wrong (p. 303), and Sway (p. 10-24). While Invisible Gorilla and Being Wrong mention Tenerife anecdotally, Sway spends several pages explaining the anatomy of the disaster with three principles:

Loss aversion (our tendency to go to great lengths to avoid possible losses), value attribution (our inclination to imbue a person or thing with certain qualities based on initial perceived value), and the diagnosis bias (our blindness to all evidence that contradicts our initial assessment of a person or situation).

Sway’s explanations seem good enough, but it bothers me to see something like an airline disaster be explained by a few psychological principles. In isolation, each of the three principles make sense and have been empirically demonstrated a number of times. However, when it comes to something much more complex, like an airline disaster involving a huge number of inputs, I am skeptical of the explanatory power of a few psychological tendencies. In other words, aren’t there more forces at work than loss aversion, value attribution, and the diagnosis bias?

What about confirmation bias – the tendency to look for what confirms our beliefs and to ignore what contradicts our beliefs while disregarding the truth.You could say that in the minutes before van Zanten took off he only looked for indications of a safe take-off and ignored indications of a dangerous take-off.

Then there is cognitive dissonance – the tendency to hold on to an erroneous belief in the face of overwhelming contradictory evidence i.e., doomsdayers. You could also say that as van Zanten became more committed to taking off, it became increasingly difficult for him to change his mind.

Could there be more? Or are we missing something?

The point I am driving at here is similar to the one I made a few posts ago regarding Joshua Bell. That is, what does it mean for psychology to explain real-world phenomena? Put differently, what does it mean for something to be “explained” or “understood?” (and keep in mind van Zanten wouldn’t be able to help us nearly as much as you think, self-reports are almost never accurate.) I don’t know; but it is important that the popular psychology literature doesn’t get too gung-ho with their psychological explanations. 

ResearchBlogging.orgKahneman, D., & Tversky, A. (1979). Prospect Theory: An Analysis of Decision under Risk Econometrica, 47 (2) DOI: 10.2307/1914185

JONES, E. (1967). The attribution of attitudes Journal of Experimental Social Psychology, 3 (1), 1-24 DOI: 10.1016/0022-1031(67)90034-0

14 Comments Post a comment
  1. Torbjörn Larsson, OM #

    “what does it mean for psychology to explain real-world phenomena?”

    That would be the same as explanation elsewhere, uncover mechanisms that can predict outcomes. If not, there is no explanation, but attempts of “just so” story telling. I don’t think you can get around any of that.

    As for predicting individual behavior, it would be impossible since all we would have is statistical laws. So we need to put Van Zanten in a group of pilots taking off. Then he is an outlier (even if restricted to fog take offs et cetera), outliers happens, and there is no specific explanation needed or wanted.

    [I am actually a little baffled why anyone would think otherwise? Maybe it is “common sense” to dismiss outliers, maybe it is philosophy to expect “causes” instead of causal (correlative) mechanisms, but it doesn’t make any of that more real.]

    Now if you go on to discuss diagnosis of individuals for medical purposes, that would change. I believe medical diagnosis have something like ~ 80 % success (dunno about psychology), and there is a requirement for the doctor actually meeting the person.

    In any case, 20 % failed predictions accommodates many van Zanten, and that is still without narrowing it down to individual events.

    August 3, 2011
  2. sammcnerney #

    Psychology just isn’t in the business of “uncovering mechanisms that predict outcomes.” At least not right now in 2011. They are interested in uncovering cognitive mechanisms, yes, but not to predict what we do – to understand what we do. So I think it is wrong to say that a psychological explanation is the same as an explanation elsewhere.

    The “just so storytelling” you mention is absolutely an explanation. True, it is not one with predictive power, and in the case of this blog post, it is discussing an outlier as you have pointed out. But nonetheless, psychologists are trying to explain what happened at Tenerife with a series of principles or tendencies.

    Let’s treat “explanation” broadly here. There are historical explanations, mathematical explanations, and psychological explanations. The way I see it, mathematical explanations are the only ones with true predictive power (1+1=2 with always be true), while the other two have heavy doses of speculation.

    One thing you are correct on – it is impossible to predict individual behavior.

    August 3, 2011
  3. Matto #

    As someone who works in the air traffic industry I recall reviewing the Tenerife disaster as part of my training. It is often used a case study for the James Reason “swiss cheese” model of disaster causation.

    Insofar as psychological factors go it also interesting to note the role of the first officer Klaas Meurs. Mr Meurs knew the albeit more credentialed van Zanten was in error yet did not sufficiently speak up. The aviation industry has since initiated efforts to create an operational hierarchy that while recognizing the role of the Captain as in command also recognizes the role of the first officer as sober second thought and the importance of having an environment where it is encouraged to speak up.

    August 3, 2011
    • Arjen #

      “Mr Meurs knew the albeit more credentialed van Zanten was in error yet did not sufficiently speak up. ”


      You really believe the story written by non-scientists? No reference to an expert in report? It is interesting why you believe in GOD investigators, it was all money, money, money ….

      You have only one chance to speak to your God, what would you say:

      “Wait a minute (poor translation is should be second), we do not have ATC-clearance”


      “Wait a minute (poor translation is should be second), there is a big big big 747 on runway”

      Interesting question is, why is hardly no one interested in missing things in report?
      – no description of other takeoffs, did Van Zanten take off as everyone else that day?

      Read appendix 3 ALPA report, a clearance is missing, no investigator noticed?

      August 17, 2019
  4. sammcnerney #

    Yes, there is a handful of psych literature on what I think is called the “Cockpit Resource Management,” which is a fancy way of saying that the pilot is not God. I believe that the drastic reduction of airline crashes in the past few decades has been attributed to CRM.

    August 3, 2011
  5. laz #

    one sees the same operational hierarchy in the operating room, where the staff is reluctant to speak up even when more than one person sees the potential error…having witnessed this, I am of a mind to say that it is not that the individual as such is seen as ‘god’ but that it is the environment (as in the operating room itself) that defines who gets the role of ‘god’…outside the room, the surgeon is not held to such a high esteem..especially if he/she has made a mistake.

    November 5, 2011
    • Hola, Spanish Talk, and thanks for your comnmet. That’s a very interesting site and blog you have there, and well worth a visit. I’ll add you to my links.Your recipe for tortilla espanola is especially apt, given my photo above. It’s long been a favourite of mine, too. And I think my running friends will be keen to try it out, tambien

      February 7, 2013
  6. So Ironic. Van Zanten goes attends a safety course, then crashes a KLM 747 into a Pan Am 747, killing 583 in the end.

    December 3, 2014
  7. Adrian Hernandez #

    Impulsive behavior is the only possible answer here because nothing else makes any sense at all, under NO circumstances does an experienced Captain just ignore all and goes for it, all he had to do was double check, ask the tower once again…. Are we clear for take off? That’s it! Couldn’t do that?

    June 7, 2016
    • Arjen #

      Did he ignore everything?

      Why did investigators ignore following communication in CVR’s?

      1703:29 RDO-2 eh would you confirm that you want the Clipper one seven three six to turn left at the third intersection? (emphasis on third)
      1703:36 T Third one sir, one two three, third, third one. (wiper off)
      1703:40 RDO-2 very good thank you.
      1703:47 T Clipper seven one three six report leaving the runway
      1703:55 RDO-2 Clipper one seven three six.

      The latter one is a confirmation, a confirmation of what?

      Why did investigators ignore other takeoffs that day?

      Why did investigators ignore appendix 3 ALPA report, a clearance is missing.

      Why did controller not inform KLM and PanAm?

      Why did investigators not tell the truth about the squeal? Half-duplex, talk OR hear, while controller had transmitter AND receiver, he could talk AND hear.

      How do we know controller did know PanAm was on runway?
      Papa Alpha … (wrong call) … report runway clear (wrong call, did he expect a yes?)

      The last calls, the controller was wrong with flight numbers, weird …

      Want if KLM crew AND controller thought PanAm was of runway? Controller did not know where PanAm was, after ATC clearance was confirmed, PanAm could have been at end runway. PanAm crew knew where they were, controller did not …

      Controller called KLM “Standby …” and later PanAm, AFTER he heart pilot PanAm scream NOOOOO.

      Controller could talk AND hear.

      August 17, 2019
  8. Arjen #

    Interesting blog, it there any proof Van Zanten took off in a different way as the other pilot that day? This is completely missing in the reports. Appendix 3 of ALPA report, is a report of German pilots who just took off before the disaster. Can anyone explain why investigators did not notice a type of clearance is missing in report?

    The squeal is explained in report, but who did do the analysis? No names at all in report, report does not explain at all why squeal started when PanAm pilot started call, and ended when co-pilot did finish call.

    it is also interesting how people can explain behavior of people on the hand of a couple of sentences. In physics, in chemistry etc etc, we do need so much data, and in this case people do believe what is said without having enough data. Impressive … does describe another incident with a 747, they got same clearance as Van Zanten, they did take-off as well. In whole investigation report no one notices that take-off was not according to the book …

    What was Van Zanten’s mistake, that he did do what everyone else did do that day in Tenerife, or that he did not follow a book?

    Why did investigators on purpose explain in the wrong way, why they thought KLM crew was sure PanAm was of runway ….

    The KLM co-pilot said: “Wacht effe”, was translated to “Wait a minute”, the correct one is “Wait a second”. But … did Van Zanten do anything weird? According to official report, Van Zanten did not decrease power, no he increased power of engines 3 and 4. Why did investigators ALPA report lie? Perhaps, very interesting for people who like psychology ….

    Van Zanten did not do anyhting weird, a 747 is a big one, issues with steering (nose-wheel) were known, You do not want that one side has more power then the other side.

    Everyone knows there were clouds, he wanted to be ready, Engines running in the right way, clouds, no centerline lights, you do not want to get problems with steering, because engines were not set correct.

    And the KLM technician was President of the European Flight Engineer’s Organization, 50% more flight out hours than pilot, why did investigators want the public to believe he was a little boy?

    Why did the PanAm pilot open call on radio and said NO and then closed call? After incident PanAm pilot said that he was worried because he was afraid that KLM would see it as a clearance to take-off.

    Most interesting is why lot of people in psychology world are very interested in an explanation once given, but are not interested in facts at all.

    Hello people, we have internet these days, we can read the CVR;s ourselves, the reports ourselves.

    Squeal is very nice explained, they explain it with half-duplex radio communication ,,, but controller had transmitter AND receiver …. He could talk AND hear …. Why did he call KLM, when he heart PanAm talking?

    August 17, 2019
  9. May I simply say what a comfort to uncover somebody who actually knows what they’re talking about over the internet. You definitely know how to bring an issue to light and make it important. More and more people must look at this and understand this side of your story. I can’t believe you’re not more popular because you definitely possess the gift.

    April 10, 2020

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