Suicide and mass murder are not the same thing. Depression, among other things, causes suicide. Causes of mass murder, in almost every case, are unfathomable. Is that why the media turns so quickly to depression when they write about Andreas Lubitz’s murder of one hundred fifty people, including himself?

Out of the need for control comes a need for explanation. The focus on depression implies that Lubitz wanted to kill himself, and that he chose a method where, from his point of view, collateral damage would occur. That way of thinking – suicide conjoined with mass murder – is unfathomable in its own right. If Lubitz wanted to kill himself because he was depressed, he had many other ways to do it. Perhaps he just wanted some company. You can see the need for explanation in everything we say.

Black swans are unpredictable and uncontrollable. The film Black Swan is about a ballet dancer who loses her mind as she dances the lead in Swan Lake. The bird has become a symbol for something that is bad, unpredictable, and rare. These qualities all apply to Lubitz’s murder of people who had committed themselves to his care. They trusted him to look after their safety, even though they had not met him. Instead he drove them into the side of a mountain.

Here’s a lesson to be drawn from this terrible event: do not become too focused on one thing. Post-9/11 airline safety focused on one problem, how to keep murderous hijackers out of the cockpit. Do not permit a person bent on death to gain control of the aircraft. No one thought, at the time, what if the person bent on death already controls the aircraft? What if a crew member wants to crash the plane into something?

Some pilots indicated they did not feel so comfortable stocking weapons and ammunition in the cockpit. We’re pilots, they said, not security officers. They raised questions of training, safety, and effectiveness. It was not clear that placing one or more loaded handguns close to the plane’s controls would do the job.

So the engineers looked at other solutions. They developed lockout mechanisms. With a simple flick of a switch, the pilot or copilot could lock the door from the inside. That way no one, including a murderous hijacker, could enter the cockpit and gain control of the aircraft. Lubitz used the lockout mechanism to prevent the Captain Patrick Sodenheimer from reentering the cockpit after he went to the restroom.

German prosecutors wonder whether Lubitz put something in Sodenheimer’s coffee to force him to go to the bathroom. Whatever happened in those last minutes of the flight, we know Lubitz acted according to a plan he conceived well before Germanwings flight 9525 took off from Barcelona. It is a plan that the engineers who designed the lockout mechanism for the plane did not anticipate.

No matter how unexpected the scenario that brought down flight 9525, why would a design team create a system that prevents the captain of an aircraft from entering the cockpit? We have identified one factor that could lead to such a mistake: focus too much on one thing. It is a well-known mistake in chess, sports, and most importantly, in safety analysis. If you focus too much on one thing, you will miss possibilities that can lead to disaster.

The people who designed the lockout mechanism for airline cockpits did not need to anticipate a mentally ill copilot bent on mass murder to avoid the mistake they made. The could have said, “We have this whole category of unpredictable scenarios, possibly rare but clearly safety related, that could require the captain of the flight to gain entry to the cockpit. We have to create a system where, under no circumstances, could the captain be locked out of the cockpit. For example, the pilot must have a four-digit security code to enter at the keypad if he or she is locked out of the cockpit.”

You could say that the pilot might be the mentally ill person bent on mass murder. That’s fair enough, but in that event you think about rules that require two people in the cockpit at all times. You may want to have that, too. You might want a system where the copilot has the security code for emergency entry. What you would not want, under any scenario, is a situation where the flight’s commanding officer cannot gain entry to the cockpit.

9/11 spawned a huge number of bad results. Response to those attacks has been almost uniformly terrible. For the Germanwings flight, blame for mass murder falls entirely to Andreas Lubitz. Nevertheless, we can still try build safety measures into aircraft that take into account all possibilities, not only possibilities we fear as a result of events on 9/11. To account for all possibilities, designers need to think not only about what they want to prevent, but also about what they want to assure. In this case, you want to assure the commanding officer’s access to the cockpit, no matter what dark plans someone has hatched.

Update

Germanwings Crash Exposes History of Denial on Risk of Pilot Suicide

DÜSSELDORF, Germany — When Andreas Lubitz sent an email in 2009 seeking reinstatement to Lufthansa’s flight-training program after a monthslong absence, he appended what in retrospect was a clear warning signal about his fitness to fly passenger jetliners: an acknowledgment that he had suffered from severe depression.

The above article and opening paragraph appears on the front page of Sunday’s New York Times, dated April 19, 2015. In a way, I can understand the focus on Lubitz’s depression and suicide. It jumps out at you. We have documentary evidence. We believe that because severely depressed people may be a danger to themselves, they may be a danger to others as well. We do not want a severely depressed person to fly passenger jets.

But think this one through. We know of no connection between depression and mass murder. The Catholic church may call suicide a mortal sin, but suicide is not a crime. People who want to commit suicide have a lot of different options. You might argue that of all the options available to Andreas Lubitz, flying a passenger jet into a mountain side appeared most doable. If that was the case, though, you want to ask why he did not fly a smaller plane, not loaded with other people, to accomplish his aim. Did he just want company in his final act?

That last question is not entirely flippant. He may have thought, “I don’t want to go out by myself.” A thought like that is not the result of depression. A thought like that is the result of going mad. Lubitz was not of healthy mind – that is, not sane. Neither depression nor madness are healthy states of mind. We have to see that whether or not Lubitz was depressed when he resolved to destroy himself and his plane, the passengers lost their lives because he was mad – out of his mind – not primarily because he was depressed.

Now you might say that depression leads to madness. Of course one unhealthy state of mind might lead to another. Yet a person can certainly become mad without being depressed first. A person can be depressed without going mad. In general, depression is far more common than madness. Whether Lubitz’s depression in 2009 had anything to do with his going mad in 2015, we cannot say. Significantly, people who report on his crime assume a close connection between his problems in 2009, and the mass murder he committed six years later.

I just want to emphasize that we are not talking mainly about a case of suicide here. True enough, Lubitz ended his own life in the French Alps. Still, he committed mass murder just as suicide bombers by the dozens commit mass murders. We do not wonder whether suicide bombers in Baghdad were depressed. Yes, suicide bombers commit mass murder as acts of war, whereas Lubitz’s act was disconnected from any conflict or symbolic meaning. That makes it all the more inscrutable. We cannot tell why he did it.

We can speculate about why Lubitz committed suicide. We can assert that depression in this case led to madness. Yet we cannot explain why this pilot committed mass murder. He did not leave a testament to explain why, nor did he say anything to his family or friends before Germanwings flight 9525 lifted off from Barcelona airport. To treat Lubitz’s actions on flight 9525 simply as a case of suicide with collateral damage misses a much larger question. That question is, what motivated him to kill those people?