The cabin temperature controller in commercial airlines, controls the cabin temperature. But if for any reason, it does not function, does the pilot have to make an emergency landing, or can he cruise to a lower altitude for normal temperatures?

  • 2
    $\begingroup$ Probably not, unless the pressure / air renewal is also malfunctioning (systems are related). $\endgroup$
    – mins
    Apr 27, 2016 at 10:42
  • 5
    $\begingroup$ At the worst this would be a "pan pan" situation, not an emergency but I can't see a malfunctioning air conditioning being that much of an issue. Typically there are enough bodies on board to keep it relatively warm at any altitude. If the passengers were extremely uncomfortable the pilot may ask to divert but that in-of-itself is not an emergency, and would probably make for a short airline career if the pilot declared an emergency for malfunctioning air temp controls. $\endgroup$
    – Ron Beyer
    Apr 27, 2016 at 12:11

1 Answer 1


I'll use the B757 as an example, on it you would not divert due to temperature control issues. In fact the Master Minimum Equipment List items 21-61-1 and 21-61-2 give permission to dispatch the aircraft with inoperative zone temperature control.

The Quick Reference Handbook (PDF) for the 757 gives the following instructions for failure of zone temperature control.

flight deck checklist

Cabin checklist

I also think most airlines and crew think passengers would rather get to where they are going than being comfortable.

As for the emergency landing, aircraft can and do divert all the time without declaring an emergency (Mayday) or urgency (Pan-Pan). So worse case the crew would choose to divert to a suitable airport.

  • $\begingroup$ This is just the zone control failing, with packs still providing air of reasonable temperature. If the packs themselves go haywire and start outputting air of unreasonable temperature (too hot is more likely), you've effectively lost them and have to divert. Of course you have two, so it is unlikely both fail unless one was inoperative from the start. $\endgroup$
    – Jan Hudec
    Apr 28, 2016 at 6:07
  • $\begingroup$ @Jan Hudec I agree if you lost both packs you would most likely divert. The more pressing issue would be the loss of pressurization. The packs do have their own, independent temperature controllers, as well, with an extra back-up controller. I did narrowly interrupt the question to mean just the cabin temperature control, though. $\endgroup$
    – OSUZorba
    Apr 28, 2016 at 17:37

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