[Zealotux]

It's possible for the pilot to depressurise the plane and use their dedicated oxygen system to breathe while everyone else on board will pass out after using their individual masks.

Doing so will give them 60-90 minutes of extra air, the passengers' masks don't last that long.

[korm]

The crew had 13 hours of oxygen supply for two pilots.

[akira2501]

The supplemental oxygen system was recharged just before this flight as well, so it was at maximum capacity.

[Cthulhu_]

What legitimate reason would a pilot have to depressurize a plane at altitude, incapacitating or killing the passengers? Just wondering if and if so why that system / function is available.

[stephen_g]

If some part of that system was on fire or an engine was damaged and it was pumping smoke into the cabin. Basically every system can be switched off, sometimes it’s necessary to be able to switch them off completely (normally for pressurisation they would already be on the way to a breathable altitude), or to be able to power cycle something to try and fix an issue.

At the end of the day, there are so many other ways for the pilots to down an airliner and kill everyone, they are ultimately the only people you can’t practically have the system distrust. The only thing you can do is the rule to always have two people in the cockpit but it doesn’t always help.

[quench]

It's more that they have the ability to control the pressurisation manually in case the automatic system fails.

Ultimately the pilots have to be able to turn anything off that might malfunction.

[quench]

It's more that they have the ability to control the pressurisation manually in case the automatic system fails.

Ultimately the pilots have to be able to turn anything off that might malfunction.

Also even if you (try to) take capabilities away they are by definition quite smart people and could probably figure a way round if they really wanted to.

[thowawatp302]

The pressurization system takes bleed air from the jet turbines so they need to be able to shut it down in the case of an engine fire

[Loughla]

I have that same question. Why is there a "kill everyone on board" setting?

[Zealotux]

Pilots have access to virtually all critical systems on board; if they wanted to kill everyone on board, they could simply fly the plane into a mountain. Pressurization is mostly automatically managed, but if it fails, the pilots must be able to manually depressurize before landing.

[ceejayoz]

Because sometimes that setting is also the “save everyone on board” setting.

[gosub100]

Because if you have control of the aircraft you already can kill everyone if you wanted. Manual control of cabin pressure could be useful if the pressurization system malfunctioned and needed to be manually overridden.

[izacus]

Same reason the engines have "kill everyone on board" setting. You know - "shut down".

[zaxomi]

All vehicles that can be steered have that possibility, even cars: If there is a steering wheel, it is possible to deliberately crash the vehicle. If it is possible to shut down engines, it can also be used for malicious purposes. In other words, there is always the possibility of using everything for malicious purposes.

On the other hand, the ability to shut down a system that has failed can save everyone on board.

There are approximately 40,000,000 flights each year. Almost all occur without incident. In the entire 120-year history of aviation, only a few accidents have resulted from the pilot intentionally crashing the plane.

[andrecarini]

Extinguishing a fire is one that comes to mind.

[wkat4242]

Yeah this happened on that Helios flight. Although not on purpose.

[heavenlyblue]

Do you mean underwater? Apologies it's not clear if it's a joke?

[Hackbraten]

Most people can’t breathe at high altitudes due to insufficient air pressure. That’s why airplanes are usually pressurized.

If that extra pressure goes away for whatever reason, people are handed oxygen masks and tanks to help them stay alive. What the GP comment says is that the plane may have been depressurized at one point at high altitude. The pilot’s oxygen mask is usually designed to last longer than any of the other passengers’s masks do. So it’s not entirely implausible that the pilot can still guide the plane into controlled descent, while all the other passengers may have already passed out due to lack of oxygen.

[krisoft]

> Most people can’t breathe at high altitudes due to insufficient air pressure.

Not most people. Nobody can breath if the altitude is high enough. There are some individual variability in how high is too high. That is of interest if you go mountaineering, but not really in a situation where an aircraft rapidly decompresses at the altitude MH370 was speculated to be flying at.

[JumpCrisscross]

> Not most people. Nobody can breath if the altitude is high enough.

Read generously, they're talking about with supplemental oxygen. At 35k feet, even with pure oxygen, many people will not be able to breathe and most will not be able to comfortably. (Above 40k feet, supplemental oxygen no longer works--everybody needs pressurised oxygen.)

(Obviously nobody can breathe above the Armstrong limit, but that isn't relevant with a commercial airliner.)

[nprateem]

I think I saw a YouTube video of a guy in a chamber simulating what happens. Basically you have less than 30s before you enter a state of delirium in which it doesn't seem important to put your mask on, so then you die.

That's why they tell you in safety briefings to always put your own mask on before helping others.