Previously, we've had minor freak-outs upon learning that people habitually steal airplane lifejackets and the flight crew will refill your water bottle if you ask. But have you ever wondered if pilots stay awake the whole flight, or if anyone's touched your complimentary pillow before? [Spoiler alert: LOTS of people have.]

A curious Reddit user asked airline professionals for behind-the-scenes details about flying we might not already know. The answers (from flight attendants, pilots, engineers and frequent fliers) revealed a series of secrets you're going to wish you never knew... either because they're so useful, or because they're so utterly revolting.

We've added a few of our own world-rocking facts to the list, and we've gotta tip our hat to Viral Quake for posting some of the Reddit thread's most startling secrets. We should also mention the validity of individual Reddit comments can't be completely confirmed.

That being said, we're already thinking about flying from a whole new perspective.

Dim lights are meant to prepare you for evacuation, not sleep.

"When a plane is landing at night, they dim the interior lights incase you need to evacuate upon landing... your eyes are already adjusted to the darkness so you'll be able to see better once outside the plane." --@bonestamp



You can unlock a lavatory from the outside.

"You are able to unlock airplane lavatories from the outside. There is usually a lock mechanism concealed behind the no smoking badge on the door. Just lift the flap up and slide the bolt to unlock." --@threeway



You're breathing engine air*.

"The air you breathe on an airplane is actually compressed air taken from the engines. A large portion (25% to 50%) is blown in the flightdeck, the rest is for the passengers. The air leaves the airplane via a small hole in the back of the fuselage." --@virgadays

*Well technically, you’re breathing air from the engine’s compressors, not the engine’s exhaust. Boeing's website explains that air from the engine’s compressors helps to warm and pressurize air from outside the plane. This treated air is then circulated into the cabin for you to breathe.

Those blankets have NOT been washed. Also, there's a solid chance your tray table has poo on it.

"I worked for Southwest as a flight attendant. Those blankets and pillows? Yeah, those just get refolded and stuffed back in the bins between flights. Only fresh ones I ever saw were on an originating first flight in the morning in a provisioning city. Also, if you have ever spread your peanuts on your tray and eaten, or really just touched your tray at all, you have more than likely ingested baby poo. I saw more dirty diapers laid out on those trays than food. And those trays, yeah, never saw them cleaned or sanitized once." --@melhow44

This is partly true, says active flight attendant and HuffPost blogger Sara Keagle. Keagle told us that in her airline’s coach class, freshly washed blankets are only supplied to the first flights of the day; after that they’re just folded and re-used. She also says tray tables are cleaned only “about once a day, usually when the aircraft RONs (remains overnight).”

The captain is allowed to arrest you mid-flight*.

The captain has almost limitless authority when the doors are closed. He is allowed to arrest people, write fines and even take the will of a dying passenger." --@virgadays

*We spoke with several flight attendants, each of whom stated that while this isn't true, the captain has the ultimate authority on a plane, though he can’t actually perform an arrest. Airline expert Chris Lopinto explains that in an emergency, the pilot may call authorities to meet the plane once it lands, and they’ll arrest any unruly passengers who are onboard. “The captain…can put you in restraints for the authorities to pick up on the ground if there is a problem, but the captain can’t ‘arrest’ you in the legal sense of the word,” he says.

You can be upgraded to first class after takeoff.

"Yes, we can upgrade you to business class or first class after the airplane's doors close. No, we don't do it very often, partly because on some airlines we have to file a report explaining why we did it, partly because there has to be a meal for you and partly because the forward cabins are often full. Who do we upgrade? Not the slob who's dressed in a dirty tank top. It helps if you're extremely nice, well dressed, pregnant, very tall, good looking, one of our friends or all of the above." --Anonymous flight attendant



Pilots fall asleep while they're flying*.

"Between 43 and 54 percent of pilots surveyed in the U.K., Norway, and Sweden admitted to having fallen asleep while flying a passenger plane."

*Seasoned flight attendant Tracy Christoph says that on longer flights, pilots are assigned to take rest periods while their co-pilot mans the controls. However, about half of pilots in this recent survey said they had indeed fallen asleep “involuntarily” during a flight.



People steal the lifejackets.

"People take those life jackets, located under or between your seat, as souvenirs. It's a vile and punishable offense, and while airlines do check each seat at the start of every day, a plane could make several trips in a day, during any one of which a passenger could steal a life vest. So, I learned, it's a good idea to check if the life jacket is indeed there." --George Hobica, airline expert

There are hold-on handles in case flight attendants get shoved off the plane.

"Next time you get on a plane, take note of the handles by the door, just inside the plane. What on earth are those for? Correct, they're grab handles, but why? Well, in a panicked emergency evacuation, when the flight attendants are manning the exit door, passengers, in their mad rush to get off, have a tendency to push them out of the way, sometimes all the way down the slide. The handles are there to make sure that the flight attendants stay on the plane if that's what they need to do." --George Hobica

You can ask for the whole can of Coke.

"If you've got a thirst that's going to take more than a few tablespoons of soda to quench, consider politely asking your flight attendant for the whole can. Most of the time, they're happy to oblige." --Beth Blair, former flight attendant

Those masks only give you 15 minutes of air (kinda*).

"If the oxygen masks drop down, you only have about 15 minutes of oxygen from the point of pulling them down. However, that is more than enough time for the pilot to take us to a lower altitude where you can breathe normally." ----@jezalenko

*"Typically, as soon as the masks come down, the pilot descends to as low an altitude as possible and finds the nearest airport to land," says George Hobica. Generally speaking, getting to an altitude where you can breathe fairly normally takes between 10 and 20 minutes, depending on the plane's altitude when it depressurized.

Flight attendants sometimes withhold your dinner, hoping you'll fall asleep.

"On night flights, we sometimes hold off on meal service as long as we can so that you'll be asleep and we'll have less to do." --Anonymous flight attendant



You shouldn't even TOUCH plane water*.

"Do not EVER drink water on an aircraft that did not come from a bottle. Don't even TOUCH IT. The reason being the ports to purge lavatory sh*t and refill the aircraft with potable water are within feet from each other and sometimes serviced all at once by the same guy." --@gruntman

*While the exact water refill process probably varies by airline, the Wall Street Journal ran a test of tap water from 14 different flights in 2002 that found bacteria levels “tens, sometimes hundreds of times above U.S. government limits.”

The cabin crew doesn't get paid until you take off*.

"Our airline used to pay us when we showed up for duty at the airport. That was eons ago... Now we get paid only when the wheels leave the ground. We don't even get paid when we're taxiing! There can sometimes be hours of delay between the time we show up for work and when we're airborne. Different airlines have different policies, but it's a way for them to save money." --Anonymous flight attendant

*Airlines may have differing policies on pay: some may pay once the cabin door is closed, and some may not pay until the plane has left the ground. Captain Laura Russo told us that at her airline, United, the crew is paid once the plane “departs the gate”-- meaning that if takeoff is significantly delayed after the passengers board, flight attendants are paid for that time.



Pilots get served separate meals in case one makes them sick*.

“Two pilots are served different meals and cannot share, this is done in case of food poisoning.” --@Wrestlingisgood



*This is indeed a smart idea and might be true at some airlines, but it’s not an industry rule. Says Captain Laura Russo, “meals between pilots are often identical, and there is no stipulation otherwise.”