Could a pilot of an airliner incapacitate everyone outside the cockpit by somehow triggering a loss of cabin pressure while simultaneously disarming the airplane's oxygen masks, manipulating the air circulation system to induce hypoxia, or some other means?

For example, would it be a credible theory that the pilot de-pressurized the 777 flying Malaysia Airlines Flight 370 and flew it off somewhere?

  • $\begingroup$ I think that you question is kind of irrelevant with todays hardened cockpit doors. Even if the passengers were aware of what was going on (and unless there was some kind of flight tracking displays in the back they very well might not be), they still can't get into the cockpit. $\endgroup$
    – Lnafziger
    Commented Mar 15, 2014 at 19:25
  • $\begingroup$ @Lnafziger- Right, but if you had trained crew locked out of the cockpit for that long, would there not be a way for them to signal distress somehow? $\endgroup$
    – Yarin
    Commented Mar 15, 2014 at 19:27
  • $\begingroup$ Well, your question is "Could a pilot of...." so I am assuming that the trained crew is still in the cockpit, not locked outside of it. :) $\endgroup$
    – Lnafziger
    Commented Mar 15, 2014 at 19:31
  • $\begingroup$ @Lnafziger - no, the scenario im putting forth is a sole operator, either one of orig pilots or another, commandeering the cockpit and incapacitating others on board, including rest of crew. $\endgroup$
    – Yarin
    Commented Mar 15, 2014 at 19:35
  • $\begingroup$ Well, what I am saying is that the "seemingly executed without resistance" bit... If the pilot is locked away in the secure cockpit, there isn't much that anybody in the back can do. Since the pilot shut off the communication equipment they could also have shut off the satellite phones that are in the back. There's no way for people in the back to communicate unless the airplane flew low enough for cell phones to work. $\endgroup$
    – Lnafziger
    Commented Mar 15, 2014 at 19:37

5 Answers 5


The answer depends on what kind of aircraft you're talking about, and how much control the crew has over the pressurization systems.

For example, in theory you could very well reduce or completely shut off the air to the cabin on a 777. This could also be done by a single crew member alone. The pilots have full control of this system should say the one of the engines produce bad air to that cabin and would needed to be switched off.

As for the oxygen masks- these are for emergency descent use and have a generator that runs out after about 15 minutes. The crew bottles last a bit longer I think, but these will also have a limit, and doing any attempt to break through the bullet-proof cockpit door in those conditions I'd imagine would be very difficult, since I'm not sure you're still picking up the amount of oxygen you normally would.

For a similar situation (though not a deliberate attempt) you can read up on Helios Airways Flight 522.

For an idea of how the pilot masks look, see this video.

Source: SmartCockpit

  • $\begingroup$ @Manfred- Yes the Helios crash is what got me thinking about this. But in this case would the pilot have a way of maintaining cockpit pressure so they wouldn't pass out themselves? $\endgroup$
    – Yarin
    Commented Mar 15, 2014 at 19:24
  • 2
    $\begingroup$ cockpit pressure is equal to cabin I believe, and it may be that the pilot supply lasts longer than the passenger's supply $\endgroup$ Commented Mar 15, 2014 at 19:27
  • 3
    $\begingroup$ @Yarin if it was an act of a single crew member he'd also have access to the ration of three crew members, further prolonging his advantage. $\endgroup$ Commented Mar 15, 2014 at 19:29
  • $\begingroup$ There is the issue though of altitude decompression sickness, especially with prolonged exposure to these conditions if they have not breathed 100% oxygen throughout the flight: clusterballoon.com/assets/… $\endgroup$ Commented Mar 16, 2014 at 1:25
  • $\begingroup$ And if the pilot really did climb to 45000 feet as reported, he would only need to depressurize temporarily, as it would have quickly been lethal to those without extended oxygen supplies $\endgroup$
    – Yarin
    Commented Mar 16, 2014 at 18:50

Yes, I think it would be very easy for the pilot in command of a 777 to do this — here's one scenario:

  1. Ask the copilot to get a glass of water and lock the cockpit door behind him
  2. Don and activate the oxygen mask
  3. Close the engine bleed air valves that supply cabin pressure
  4. Open the controlled outflow valves to equalize cabin pressure to altitude pressure
  5. Put the passenger/supernumerary oxygen to "reset" (or pull the circuit breaker)
  6. Ascend a little bit above the service ceiling of FL 410.

At FL 450, consciousness is measured in seconds, death in about 4 or 5 minutes.

  • 5
    $\begingroup$ I read somewhere that Flight 370 flew at FL 450 for 45 minutes. I wonder if it is coincidence that the 3 flight O2 supplies 15 minutes each? 3 X 15 = 45? $\endgroup$ Commented Mar 17, 2014 at 17:22

Very simple operation and you don't need to be at 41,000 feet to do it. Anything above about 21,000 feet and you die in a few minutes; you just fall asleep.

If you are really paying attention, you would first notice your fingernails (under them) will turn blue due to a lack of oxygen first. A few giggles perhaps, then you'd pass out and DIE. Quite painlessly actually.

  • $\begingroup$ Death at 21000 ft will take hours $\endgroup$ Commented Jan 17, 2019 at 17:24

The answer is yes: if one of the pilots needed to use the restroom, regulations require the other pilot to put on his O2 mask while the other pilot is away. Once outside the cockpit, the other pilot could lock the door and the other pilot out. Then he could turn everything off.

Also since it was at about 1:30am, most passengers would be trying to sleep in their chairs; additionally the masks that drop only have enough O2 to last while the aircraft descends to a lower/safer altitude — so if the plane maintained altitude, there would only be 5-10 minutes of O2 and everyone would pass out and eventually die.

Unless it landed on smooth water, like the miracle on the Hudson, the plane's ELT (Emergency Locator Transmitter) would go off and the crash site would be pinpointed by satellites within seconds.

So therefore one of two things happened:

  1. It landed on water softly and is now at bottom of ocean, or;
  2. It landed safely on land because there was no ELT signal.
  • 2
    $\begingroup$ Yea interesting that practically no one's talking about the ELT, but it failed on Air France 447, so not clear how reliable they are in water crashes. $\endgroup$
    – Yarin
    Commented Mar 21, 2014 at 11:33
  • $\begingroup$ Ever since the LAM470 incident, it has been required that two crew members be in the cockpit at all times specifically to prevent a one pilot locking the other out like this. $\endgroup$
    – StephenS
    Commented Dec 11, 2018 at 17:17
  • $\begingroup$ re: "regulations require the other pilot to put on his O2 mask while the other pilot is away" can you provide a reference for that ? $\endgroup$
    – summerrain
    Commented Dec 11, 2018 at 19:49
  • $\begingroup$ This answer would be much better without the speculation at the end. $\endgroup$
    – Antzi
    Commented Dec 12, 2018 at 0:19

Depressurization leads not only to the lack of oxygen in the cabin (and cockpit), but likewise may lead to a dramatic drop in temperature.

For altitudes above 38,000 - 65,000 feet, the outside temperature is roughly -70°F/-55°C. Combined with data suggesting that at 40,000 feet a passenger sitting quietly would retain consciousness for only about 18 seconds with the loss of oxygen from depressurization (and thus presumably fewer seconds at 45,000 feet), it may only be a matter of seconds, not minutes, before everyone in the cabin would be dead.

What I don't know and wish I did know is whether the cabin and cockpit have separate pressurization systems. I assume so. This would make it even easier for a pilot to incapacitate/kill all crew and passengers.

  • 2
    $\begingroup$ Cabin and cockpit have the same pressure. There is no way to change that. $\endgroup$
    – user1589
    Commented Mar 18, 2014 at 7:18

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