On aeroplanes when the passenger closes the toilet door it keeps the door closed and changes the status to occupied in a separate (or sometimes the same) action as closing the door. I am wondering if there are any specific reasons that this design only applies in public transport but not in buildings.

It seems logical that when you close the toilet door there is no reason for it not to remain closed and the status changed to occupied, yet I have not seen such designs for toilets inside buildings.

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    What do you mean? When you close the folding lavatory door, it latches, but then you slide that lever to the side and it locks and the status changes.
    – Keavon
    Commented Oct 23, 2015 at 7:19
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    I have never seen an airplane toilet door that automatically locks when you close it, there is always some lever or so to lock. Otherwise what happens if someone closes the door from the outside? Similarly I have rarely seen a non-private toilet that does not have some kind of occupied indication when you lock it.
    – PlasmaHH
    Commented Oct 23, 2015 at 8:21
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    I'm voting to close this question as off-topic because it's not a UX question. (The UX of public restrooms could obviously be improved by implementing such a feature, but there's no UX reason as to why it's not. It's likely more of a code and/or money issue)
    – DA01
    Commented Oct 23, 2015 at 15:25
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    In addition, many public restrooms do do this. It's just not a large percentage so is rarer to see.
    – DA01
    Commented Oct 23, 2015 at 15:27
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    All airplane lavatory doors I have ever seen looked like this on the inside. That is, there is an explicit latch for locking the door, nothing gets locked automatically. Could you provide a photo of a lavatory door that indeed locks automatically upon being closed? Commented Oct 23, 2015 at 15:45

6 Answers 6


Here are some things that make the airplane situation unique:

  • There is a large economic benefit to having the minimum number of toilets necessary in an airplane, since toilets add weight and take up space that could be used by seats. So anything that helps increase the efficiency of toilet use (even if expensive) is likely to be justified.
  • Light-up signs showing that toilets are occupied are a necessity to efficient toilet use on an airplane, and this system works closely with the automatic locking.
  • Airplane toilets are an unfamiliar design, since they are optimised for space and weight efficiency. This increases the likelihood of customer mistakes.
  • Accidentally opening a toilet door is likely to result in physically bumping a person, since the toilet is so small.
  • Airline staff need to know definitively whether a toilet is occupied. For example, no one is allowed to use the toilet when a plane is taking off. And if someone could hide in a toilet while the plane was emptying, that could potentially be a security problem.
  • Airlines are being judged on basic amenities more than most businesses. Think about the extended rants you hear about things like seats not reclining or too many bags in overhead bins. Sitting in a cramped space for several hours seems to make the small things matter a lot more in people's mind.
  • To add to your 4th point, too - the door is more likely to "pop" open, and also in many aircraft/trains, the toilet is directly next to a seat, and therefore much more public if it is accidentally opened. Whereas most toilets in buildings are tucked down a corridor
    – Jon Story
    Commented Oct 23, 2015 at 9:53
  • Great answer. Consider too the narrow 1 - 2 isles for movement. The safety of all passengers and the efficiency of cabin crew movements are significantly increased with a toilet status indicator easily viewed from afar. Queues and necessary cabin movement is reduced with this system.
    – Dave
    Commented Oct 23, 2015 at 20:05
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    "this system works closely with the automatic locking" - airplane toilet doors ABSOLUTELY DO NOT have automatic locking. this question is sort of bizarre and the answer is also a bit bizarre Dan as it does not recognise the bizareness of the question! heh!
    – Fattie
    Commented Oct 23, 2015 at 20:55
  • All of these are true on trains, and most (#1, arguably #2, with respect to space, #3, #4, possibly #5) are just as true for toilets in buildings. In particular, #2 seems weird here - as plane toilets generally remain closed also while unoccupied (who would want the odors to spread across the cabin?), how could the light-up sign possibly know whether the toilet is closed with or without someone inside? Commented Oct 23, 2015 at 23:06

The vast majority of single-occupancy public toilets (not cubicles with a shared space outside for handwashing and drying, but a single room containing both toilet and sink) will have an indication for occupancy. I have seen this in restaurants, on trains, and in aeroplanes.

Very few such toilets (none, in my experience) will have closing and locking the door be a single action. Otherwise, it would be easy for someone to leave an empty toilet locked. Usually, there is a physical latch which can be operated only from the inside. Sliding the latch will both lock the door and move a small panel on the outside. On Irish trains, there is a little toilet symbol at one end of the carriage, so passengers know in which direction to head: this will also turn off when the toilet is occupied. Wheelchair-accessible toilets on trains have a lock button rather than a physical latch: this turns off the green light on the “door open” button on the outside.

On aeroplanes when the passenger closes the toilet door it automatically locks the door and changes the status to occupied in the same action as closing the door.

It’s a while since I’ve been on a plane, but I think that the way the door is shoved from the inside might activate an automatic locking system. This is unusual and no doubt fiddly to build (and you certainly wouldn’t want to activate it from the outside accidentally), but might be necessary on planes: if people could be in the toilet without locking the door and activating the “occupancy” notification outside, they could hide there, which might be a bad thing.

That degree of complexity is unnecessary elsewhere, so it isn’t used.

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    In US restaurants and gas stations with single occupancy, there is no indication: the door locks on the inside just the way it would in a home. The only way to tell is either the door is ajar (almost never in a public place) or you walk up, grip the handle and try to turn it both ways, then you say "sorry" and the person inside says "just a minute!". So, there is no indication. You then go away and wait a while, maybe see someone walk from that direction, and repeat. If a child is inside and they didn't think to lock it, you say "Oops!" and they get embarrassed, then you continue as before.
    – user67695
    Commented Apr 8, 2016 at 15:29

Very interesting question. I have seen doors like this outside airplanes enough that I know they do exist, usually at chain restaurants. These locks are only necessary when it is impossible for you to see if there is an occupant inside because you can't see under, over, or peak through the gap.

Otherwise the extra cost in hardware and reduced durability don't justify the benefit. (of which there is very little when you can just peak or hear)


  • Most toilet doors I know don't have a spring loaded mechanism to keep them shut automatically, so I suppose you can assume sometimes that if the door is closed then it is occupied. But if there is little justification for the cost then why are they used on airplanes?
    – Michael Lai
    Commented Oct 23, 2015 at 0:38
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    @MichaelLai On airplane, whether bathroom is in use or not, doors often stay closed. Airplane bathroom doors have tight seals around the opening that make it impossible to tell if it is occupied or not. And at 85 decibel during normal cruising speed, you certainly wouldn't be able to 'hear' most noise coming from inside either. So such indicator is a necessity.
    – Jung Lee
    Commented Oct 23, 2015 at 1:40
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    Sounds like we're talking about two separate things; 1 spring loaded door that shuts itself (not lock itself. that would be bad). 2. outside occupied indicator. Spring loaded door on airplane is a necessity because without the tension, it would flap around during plane turbulence. Just to remind folks, airplane door is bisected down the middle. youtube.com/watch?v=gDt6UkGp-Us
    – Jung Lee
    Commented Oct 23, 2015 at 5:35
  • As weird as your American gappy toilet doors are, I thought ye had them only on cubicles, not on single-occupancy full toilets (i.e., rooms which also contain a handbasin).
    – TRiG
    Commented Oct 23, 2015 at 14:12

I think the answer is easy. For those doors that have the mechanism that shows occupancy - they are or need to be kept closed by default. Mainly airplanes and portable johns in the US.

On the flip side if I go into my work restroom and the door is all the way closed I know someone is in it. It is really that simple.

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    I have discovered by visiting England that in that country, the default for bathroom doors is "always closed". So, if you want to NOT be barged in on, you MUST lock the door. In the US, the default is "always open", so if it is closed, the assumption is that someone is in there. If it stays closed a LONG time you need to knock first. Not sure how such a dramatic difference in customs arose, or why they always close the door in England even when the room is unoccupied?
    – user67695
    Commented Oct 23, 2015 at 20:26
  • Keeping the door closed keeps the smells contained.
    – TRiG
    Commented Oct 14, 2021 at 11:52

It seems logical that when you close the toilet door there is no reason for it not to be locked and the status changed to occupied

I think that your assumption here is wrong. I can think of the following reasons a toilet wouldn't automatically lock:

  1. An empty toilet, closed from the outside, is now locked with no occupant.
  2. The designers don't want to enforce the restriction of the door having to be locked when there is an occupant. Think of the example of a parent waiting outside of a small toilet cubicle, while a young child is inside. Why force a door to be locked when it is closed? The child might struggle with the lock mechanism. (Of course the child could still lock the door themselves). This may be an edge case, but it seems reasonable for the designer to assume that the occupant will lock the toilet manually if they want it locked.
  • I imagine that it would be hard to close most toilet doors from the outside, since the latch is placed on the inside. And if you can close it from the outside then you should also be able to open it from the outside as well.
    – Michael Lai
    Commented Oct 23, 2015 at 10:53
  • By "close", i meant "pull it closed" (so that a hypoethical auto-locking mechanism can activate"). Yes, if there is no handle, it might be difficult (but not impossible). Commented Oct 23, 2015 at 12:02
  • @Robominister: Since there usually is quite a gap under most ground based toilet doors, it would be quite easy to pull them with your feet.
    – PlasmaHH
    Commented Oct 23, 2015 at 12:07
  • @PlasmaHH True. I once got "pestered" by a stranger when I was (ahem) using a public toilet. They kept reaching under the door with their hands and sticking their head under and looking at me (it was an exceptionally tall gap). Now, I'm going to assume the design reason for those gaps is possibly to provide some kind of physical and visual access when someone might be stuck in there (eg passed out) Commented Oct 23, 2015 at 12:54

The best reason I can think of is that every toilet I've seen with an occupied/open indicator has been set up such that when the door is closed there is no way for other people to see inside the room.

In other stalls where there are small cracks between the walls and/or a foot or so gap from the floor you can tell if someone is inside by looking for their feet or briefly glancing through the crack to see if there is a person.

The type of toilet on airplanes is impossible to do this, you have to walk to the door and knock or try to open it.

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