Good thing I'm not a pilot!

November 18, 2007 11:17 PM

Why do I fall asleep when the airplane takes off?

I am not a person who falls asleep easy, but everytime I fly on a large airplane I fall asleep during the taxi phase and wake up 30 minutes into the air. I fly about once every 2 weeks and I've found that even coffee doesn't stop this phenomena.

I never fall asleep in cars, but do get drowsy on some trains.

Do you think it has to do with the vibrations? The pressurization of the cabin?

I'm not complaining, but I'd like to understand it more.

posted by hazel to travel & transportation (17 comments total)

One thing for me is that I'm anxious about getting going, nervous about missing various check ins, stressed by all the queuing etc. When the plane finally starts moving it is often the first chance to relax in hours. I image you get a flood of endorphines and fall asleep. Just as some people fall asleep after sex.
posted by uandt at 11:31 PM on November 18, 2007 [1 favorite]

I don't know for sure, but I would speculate that it has something to do with the noise and vibrations. On a train and a plane, these are very regular and consistent in a way that they're not on cars, and it's louder once you're on the ground.

Sensory overload can trigger a hypnotic-like state pretty easily. Usually, we notice this with acoustic stimulus, though other stimulus can do it as well. My guess would be that the combination of the noise and vibration is enough to encourage a light hypnotic (or alpha-wave, if you prefer) state that is conducive to sleep. If I recall correctly, alpha waves often (always?) precede the theta waves that characterize the lightest phase of sleep. The effect is not irresistible, obviously, and the exact nature of the effect will vary from person to person.

Again, this is just speculation. And I'm doing it while sleep deprived, so ... take that into account as well.
posted by spaceman_spiff at 11:36 PM on November 18, 2007

White noise helps people sleep, there are even machines for it. I don't know if it's a myth or not but I've used white noise to get infants to stop crying and fall asleep.

Lots of white noise during take off.
posted by Kattullus at 11:58 PM on November 18, 2007

The crew will turn on the heating and set it pretty high almost immediately after they close the doors (makes people sleepy, and a cabin full of 300 sleepy people, a significant minority of whom may have had a drink or two, is way easier to control). The heat, combined with the vibration, is probably the culprit.

FWIW, I get the same thing. I also get it on long-distance trains when the heat is up high.
posted by Happy Dave at 12:07 AM on November 19, 2007

I also always fall asleep at takeoff and also landing. Even though I try to stay awake since that's my favorite time of flight. I also fall asleep on boats. I figure it's the vibrations.
posted by Etaoin Shrdlu at 12:20 AM on November 19, 2007

Maybe it didn't start as this, but if you got used to having time to relax and fall asleep once you got on the plane, are you maybe just psychologically conditioned to it now? Subconscious says "Oh, I'm on a plane. Sleep now!"
posted by agentofselection at 1:13 AM on November 19, 2007

Don't underestimate the effect of simply having a reasonably comfortable place to sit down with nothing particular to do.

Consider also the percentage of flights where you have had to disrupt your normal sleeping routine to get on the plane in the first place. If you are a regular business traveller then I suspect you are often wanting to travel on one of the first flights into the place you are visiting so that you can achieve a full day of work there.
posted by rongorongo at 2:19 AM on November 19, 2007

I don't fall asleep during the taxi part of the flight, but I almost always get sleepy once in the air, at least for the first 30 minutes or so. I always thought that it was due to the fact that the cabin is pressurized to 8000 ft. meaning that as a sea-level dweller, not being used to the lower PaO2, that I'm feeling the effects of mild hypoxia by falling asleep.
posted by scblackman at 4:03 AM on November 19, 2007

90 percent of the time I do this on taxing, also, and wake about 30 min. later. I think it's all the stress leading up to getting there, checked in, security, etc.. I think the white noise leads to it, also.

It's an odd feeling, so I know where you are coming from.
posted by 6:1 at 4:40 AM on November 19, 2007

I get sleepy right at the beginning of the takeoff roll. It's not cabin pressure as it's still at sea level in the cabin. Also, I have some experience with mild hypoxia and it makes me not sleepy but nauseous. I tend to think it's a combination of factors already mentioned above: white noise, gentle vibration, release of stress about a possible impending delay.

I know the last factor can't be all that important, though, as every child under the age of five (who doesn't have an ear infection) is asleep before the plane gets to ten thousand feet.
posted by MarkAnd at 4:44 AM on November 19, 2007

I fall asleep during taxi and takeoff, too, and usually wake up about 20-30 minutes into the flight. However, this also happens fairly often if we have a long ground delay. I think it's mostly conditioning, as I am a frequent traveler who is often sleep deprived and my body likes to take advantage of the opportunity to sleep. I think some part of my brain just kind of associates that environment with naptime or something. I also get sleepy as a passenger in cars and on trains, so it probably also has something to do with the vibrations.
posted by bedhead at 5:41 AM on November 19, 2007

It's a lot like being in a carseat on top of a washing machine, which is a great way to get babies to sleep.
posted by macadamiaranch at 6:31 AM on November 19, 2007

Here's a GoogleAnswer to this question. It's nothing authoritative, but the theory that it's related to "fight or flight" syndrome makes sense. ("Flight" meaning fleeing, rather than flying.)
posted by beagle at 6:46 AM on November 19, 2007 [1 favorite]

for me it's that gentle g-force push at takeoff that does it. once we level off and that's gone, i'm awake.
posted by judith at 7:02 AM on November 19, 2007

Interesting. I just assumed it was a sort of lulling, in-utero environment. Infants will similarly fall asleep if you put them in a basket or car seat on top of a running washing machine. When a foetus is in the womb, it is amazingly loud in there, and there is (naturally) a lot of movement as well. I always associated the jostling of the flight and the noise of the jet engines with that.
posted by DarlingBri at 11:09 AM on November 19, 2007

I think all of these responses are good, but there is also another factor to consider...

when travelling by plane, there is a lot of hurry up and wait, line up, lug stuff around, get searched, id checked, etc... then you board and stow your stuff away, get comfortable and wait to push back from the gate to taxi out to the runway... you don't have a choice. you can't get up and go for a walk, stretch your legs, grab something from your bag in the overhead bin, use the lav,... so you're basically a prisoner in an airplane seat from the moment of pushback from the gate, then the often lengthy taxi, take off roll, and climb until the captain clears 10 000 feet and turns the seatbelt sign off. that can mean an hour of just sitting until you're ALLOWED to get up. what else are you gonna do if not sleep through the part when the cabin is pressurized and the engine vibrations and noise reach that critical point thatg makes you drowsy, and unlike in your car you can't open the window to get a blast of fresh air, or sing a song out loud to keep your mind engaged ( well you could, but people would look at you funny... )

I say this from experience as I log anywhere between 300-500 flight legs a year...
posted by dawdle at 11:18 AM on November 19, 2007

I have always heard that oxygen levels during flight are quite low and have even heard that pilots can lower oxygen levels even further during flight to induce sleepiness on passengers (I haven't been able to confirm this as of yet).

The last paragraph of this article talks about oxygen during takeoff and Air Canada has a paragraph on oxygen during flights...
posted by MrBCID at 12:56 PM on November 20, 2007