Why do I immediately get sleepy when the airplane closes its doors and pressurizes the cabin?

I’ve been travelling by air a lot more lately, and while I’m fine with air travel, I’ve noticed something.

Early flight? No problem, I’m awake and alert in getting to the airport.
Boarding? Similar. I feel normal while everyone is shuffling through and trying to find space to stow their carry-ons.

Once everyone is seated and they close the doors - well, shortly after you can feel the smallish pressure change - I assume that’s when they pressurize the cabin? And literally when I notice that, within a few seconds I get very, very sleepy. As in going from fully alert to struggling to keep my head up.

Not that it’s such a bad thing, I usually end up falling asleep for the first 30-45 minutes of any flight. Once I wake up, I’m usually back to normal, even if the flight has several hours more.

What’s going on here?

Not sure as I have felt the same, but I hope the pilots aren’t feeling the same way!:eek:

Well, they don’t actually ‘pressurize’ the cabin on the ground. I mean, you’re in a pressure sealed compartment, but they don’t increase or decrease pressure on the ground after the doors close. Once you take off and start climbing the pressure starts gradually decreasing with the altitude until around 8000 feet (I think) which is what airliner cabin pressure is set to be maintained at. Some of the newer jets keep it at 6000 feet for better passenger comfort.

So, I think it might just all be in your head! :smiley:

I get the same thing sometimes. I suspect its just an illusion. You wake up early, you have a bunch of stuff to do to get to the airport, get through security and get on your flight. Finally, you get on the plane, and you know you don’t have anything to do for several hours but sit, so you relax a bit and all the rushing around catches up with you and you get tired quickly.

When the doors close and they start the engines and get ready to push back from the gate, as soon as the external power lines are disconnected and the plane is on internal power you’ll notice that the environmental system kicks up a notch (a lot more air starts coming out of those little movable nozzles above your seat). The combination of this increase in fresh air circulation and the additional white noise of air flowing may be what makes you sleepy.

I get this fairly often too. In my case I think it’s because my job is done. I’ve either got up early or done a full day’s work, packed, battled my way to the airport, endured check in queues and security, hung around the gate, and finally made it to my seat and stowed my carry-ons. Now I need to sit down for an extended period with no internet or phone access.

Then I relax, and my body suddenly realizes how tired it is.

ETA: Or I could have read Simplicio’s post which basically said the same thing.

:smack:

If you usually sleep on flights, it could be a simple Pavlovian response.

Are you Asian ? My observation on my many flights across the Pacific is that most of the Asian passengers will sleep through most of the flight.

I am very jealous, since I might sleep for one hour of a 15 hour flight.

The wife is exactly like this and not just on planes but rather any form of transportation you can think of - buses, taxis, you name it. Myself, I find it difficult to sleep on planes and buses, but I put that down to usually being somewhat too big for the seat.

When it’s happened to me, I’ve assumed that it’s the vibration of the plane having a soothing effect. I have a similar reaction in the passenger seat of a car sometimes.

For the wife, she conks out before the vehicle even starts up. As soon as she hits the seat.

I often take Dramamine when flying, which of course has a sedative effect. I think I’ve developed a conditioned response so that even if I don’t take Dramamine I start to zone out once I get to my seat.

I do the same thing, but I’ve always just assumed I’ve conditioned myself to sleep on flights (I haaaaaaaate being bored, trapped in my little coffin of a seat on a plane).

generally this is not correct. If you have an altimeter (which I have on my watch), once the doors close the pressure is dropped to IIRC 6-8000k long before the plane is in the air.

And that I think is the answer to the OP - reduced cabin pressure = reduced oxygen availability.

This is immediately refutable from other evidence. If the pressured dropped that much, your ears would pop and your half-filled water bottle would crackle (and, if opened, would hiss). None of that happens.

There is also no mechanism present to reduce the pressure in the cabin lower than ambient. Compressed air is used to keep the interior pressure above ambient when flying, but there’s not a big vacuum unit or anything to reduce the pressure below ambient.

China Guy - So you use an altimeter to notice that cabin pressure changes “long before the plane is in the air” Couldn’t you just look out the window to determine the plane is not yrt in the air>

" increase in fresh air circulation" is usually invigorating not enervating.

Perhaps you’re just overly sensitive to the chemtrail ingredients that have contaminated the cabin.

I feel more relaxed in a yielding sort of way, like my dog does when I trim his nails.

I envy you.