No one has more insider knowledge about flying than flight attendants. Once considered a glamorous vocation, these days flight attendants can expect 4am wake-up calls and sporadic hours, delays, flight cancellations that will nix plans, plus weekends and holidays spent working. Oh, and grumpy passengers, who think nothing of short clicking their fingers to demand attention.

It’s fair to say that having an office in the sky offers a unique and stressful working environment. It’s certainly not your typical 9-to-5 job.

Whether you’re a frequent flyer or only take to the air occasionally, chances are there’s a lot about air travel you don’t know. In fact, there’s a lot about flying that many airlines don’t want you to know, and while you’re sitting there in the cramped comfort of your airplane seat, there’s a team of flight attendants hard at work keeping everyone safe, cleaning up mess, seeing and hearing everything that goes on in the sky.

Here are all of the behind-the-scenes secrets flight attendants tend to keep to themselves - and some little tidbits they are all too happy to share. Whether you want more attentive service or want to avoid getting kicked off your flight, read on for the inside scoop.

20 20. The Food Is As Unhealthy As It Seems

At best, airplane food is edible. At worst, it’s a scalding hot plastic tub of gloopy stew, overcooked rice or leathery meat and vegetables that have been boiled beyond all recognition. And it isn’t any better for you than it looks.

Even in training, flight attendants are told that in-flight meals are nutritionally useless because of the salt, sugar, fat, and simple carb content. Despite stickers claiming it is ‘freshly prepared’, most plane food is produced long before it is served to passengers - even in first class. Usually, the meals are made between 12 and 72 hours in advance but can be kept in a chilled stage for up to five days. Many flight attendants avoid tucking in at all costs.

19 19. If The Plane Door Is Open, Flight Attendants Are Not Getting Paid

Are you that passenger who spends a good 10 minutes trying to a cram a bag into an overhead locker, before getting it out again to look for your headphones, before spending another five minutes trying to squeeze it back while a smiling flight attendant offers assistance?

Next time you catch yourself faffing about and holding up other passengers, take a second to remember that flight attendants are not getting paid for this. None of that on-ground assistance shows up in their pay cheques because they get paid for flight hours only. Translation: The clock doesn’t start until the craft pushes away from the gate.

Flight delays, cancellations, and layovers affect flight crew just as much as they do passengers, so try to remember that the next time you’re frustrated.

18 18. Flight Attendants Are Still Required To Look A Certain Way

A 1936 New York Times article described the ideal air hostess as "petite; weight 100 to 118 pounds; height 5 feet to 5 feet 4 inches; age 20 to 26 years.” For many years, if you wanted to be a flight attendant, you had to be female and look like a supermodel.

These days, male flight attendants are a common sight and physical requirements are far more general. For example, reach is more important than height because staff are required to be able to reach the overhead lockers, for obvious reasons.

Airlines generally require flight attendants to be “in proportion to your height”. What might be considered a “healthy weight” may be determined by body mass index. And Several airlines are reported to have specific guidelines for the physical appearance of their cabin crew, such as AA which is said to advise that: "Noticeable hair in nostrils and in/on ears or underarms must be cut or otherwise removed.” Being well-groomed is still a must.

17 17. Flight Attendants Are The First Line of Defence Against Serious Crime

Some incidences have been thwarted thanks to some amazing, observant flight attendants reporting suspicious behaviour. Increasingly, flight crew are being trained on what to spot and how to handle any potentially illegal activity on a plane.

First up, they must notify the pilot when they suspect a victim is on board. The pilot then calls ahead to the flights' destination where authorities are notified to meet the plane. Think about that the next time you have to wait for your coffee. And on the subject of coffee...

16 16. That Airplane Coffee Is A Bad Choice

If you’re ordering a drink on board, it’s probably best to skip anything that doesn’t come from a bottle or can. In fact, flight attendants will actively avoid drinking the potable water from the aircraft.

The problem of dirty water onboard aircraft has gained a lot of attention since the eye-opening study of the Wall Street Journal in 2002: the number of bacteria in water samples from 14 of the most popular airlines was hundreds of times higher than the established standard. Today’s situation hasn’t changed a lot, so it’s better to drink only bottled liquid onboard. Tea, coffee, and water from the sink should be avoided.

15 15. No One Ever Officially Passes away On A Flight

Flight attendants are trained in CPR, first aid and defibrillation but there’s only so much they can do at 30,000 ft in the air. If a passenger were to pass away mid-flight, they can’t be officially pronounced dead until the plane lands - it’s not something flight attendants are allowed to do.

It turns out there is no one-size-fits-all rule about what to do with a dead passenger. The International Air Transport Association, which represents most of the world's airlines, advises flight crew members to move the body to a seat with few passengers nearby.

If this isn't possible, the crew members might place the body in the galley or first class - or, in the rare event a plane has one, a compartment referred to as the "corpse cupboard.” If no other seats are available, the body would most likely be left in the seat.

14 14. Those Planes Are Way Dirtier Than You Think

If you’re thinking of walking down the airplane aisle without your shoes and socks on, you may want to reconsider. During a flight, people have nosebleeds or open wounds, and not everyone can hold it in while waiting for the toilet. Yes. Ugh. And consider this, most airlines only do a "superficial cleanup" after the flight.

The dirtiest part of the plane is the tray tables, which might get a cursory wipe with a used cloth. People constantly lay their heads on tables, change babies' nappies, and rest their feet on them. And you want to eat your food off it?

13 13. There Might Be A 'Suprise' person On Board

Airplanes carry millions of travellers around the world every year, but they also ferry thousands of deceased passengers too.

A lot of freight gets shipped on commercial flights. One of these ‘freight’ items is referred to as HR during radio correspondence. HR is an abbreviation for human remains.

Truth is, some people pass away far from where they want their bodies to rest. They're packed in wood-framed, secure casket, and then encased in an air tray, as well as being accompanied by a burial transit permit or a health officer’s certificate.

An estimated 50,000 bodies are transported by plane every year and Amsterdam’s Airport Schiphol even has its own mortuary, which processes around 2,000 bodies annually.

12 12. Please Don’t Ask For A Diet Coke

Flight crew won’t ask you not to choose Diet Coke from the drinks trolly, but they’ll be quietly hoping you don’t. Of all the drinks they serve, Diet Coke takes the most time to pour because the fizz takes forever to settle at 35,000 ft.

In the time it takes to pour a single cup of Diet Coke, three other passengers can be served. It’s just a bit of a slog and one that holds up an already in-demand drinks service.

11 11. The Lavatory Door Can Be Opened From The Outside. Oh Yes.

Breaking the smoking rule? Joining the Mile High Club? You might want to think again before locking yourself in the bathroom to indulge in any illicit activity.

Flight attendants have their own keys in case a passenger is locked in the lavatory. In addition, many aircraft have the door lock mechanism itself installed under the "No smoking" sign on the toilet door. If you raise the flap and turn the bolt, the door will open. So, now you know, next time your kid locks him/herself in the airplane bathroom.

10 10. There Is No Shame In Asking For More Food

The idea of hoarding plane food might seem stingy. After all, in-flight cuisine has a pretty bad reputation - why would you want to eat more of it than is strictly necessary? But hey, free food is free food. We’re not going to judge.

It’s a little-known fact that if you’re still hungry after your first meal, it’s not frowned upon to ask for more, providing you ask nicely. The food distributed onboard an aircraft has a short shelf life since and all excess containers with food are immediately discarded after the flight. Therefore, if your stomach demands more, and there’s an excess of food leftover, flight attendants won’t mind getting you another serving.

9 9. Blankets And Pillows Aren’t Necessarily Washed, Just Beautifully Refolded

Have you ever wondered what airlines do with those lightweight blankets and masks they hand out to you? Well, if you’re a germophobe — or just don’t fancy snuggling into someone else’s snot-caked rag - you’ll want to check that the blanket is wrapped before you use it. Airline procedures sometimes mean that crews end up folding previously used blankets up before passing them out to a new bunch of passengers.

Airlines will send blankets off to be washed at an industrial facility, but for some carriers this only happens at their home base airports.

8 8. Flight Attendants Might Know More About You Than You Think

Much of the text on your boarding pass probably doesn't make a lot of sense to you at first glance, but it actually includes a wealth of interesting - and potentially sensitive - information.

The first two letters before the flight number refer to the airline. The numerical portion of your flight number is actually a clue as to what direction you'll be flying in - odd-numbered flights fly south while even numbers fly west.

Meanwhile, the six-character segment of text on your boarding pass is your booking reference or passenger name record. This little code actually can be used online to look up everything from your destination to your age and credit card information.

7 7. They Want You To Know: You Need To Keep The Shades Open

When flight attendants ask you to open the shades, do it. The emergency-exit shades have to be up during landing because flight attendants are required to assess the conditions outside before they open the door. Fire, deep water, or rocks outside the exit, for example, would make it unsafe to exit the plane, and the flight attendant would have to make that determination fairly quickly.

6 6. They Want You To Know: Lifting Your Luggage Is Not A job Requirement

There are simply some passengers, despite being an abled person, who would still have flight attendants lift and stow their own hand carry luggage unto the overhead bins. The truth is that flight crew aren’t supposed to lift luggage, though they can assist when deemed necessary for PWDs, pregnant women, senior citizens, or individuals who cannot reach.

It’s a policy requirement that makes perfect sense - one piece of luggage will not do instant damage but the consistent lifting of more than 10 to 50 every day for however many years will slowly do physical damage, which could end a career.

5 5. They Want You To Know: It Will Be Noticed If You Try To Join The Mile High Club

Seriously, getting frisky in an airplane loo? Those places are gross. But please know, any attempts to do so will be noticed by flight crew.

It’s usually the long line of people waiting to use the bathroom that gives you away, and nine times out of 10, it’s a passenger who asks the flight attendants to intervene. Strictly speaking, it’s not against the law to join the club. But it is against the law to disobey crew member commands.

4 4. They Want You To Know: You Can’t Get Wasted On Their Watch

Flight attendants are bound by their contract when it comes to serving alcohol to passengers. So when you’re feeling tipsy, it’s time to stop ringing your flight attendant for more mini bottles. They will simply refuse to serve you.

Alcohol hits passengers harder during a flight - one drink in the air can feel the equivalent to two on the ground. Plus, it is actually illegal to be intoxicated on a plane and it is illegal for flight crew to get you drunk. So, if they cut you off, don’t argue.

3 3. They Want You To Know: Landing This Gig Is Tough

Think flight attendants are just glorified waiters? Think again. It’s easier to get into Harvard than it is to become a Delta flight attendant.

When the airline announced it had 1,000 flight attendant openings for 2018, more than 125,000 hopefuls applied for the job. Yet less than 1% of them were chosen – compared to a 5.1% acceptance rate at Harvard in 2016. To work for a major airline requires submitting an application, conducting a video interview, face-to-face interviews and eight weeks of rigorous training.

Flight attendant training not only includes learning technical details of the plane you’ll be flying on, but there’s also heavy safety training, with flight attendants learning how to safely evacuate the aircraft and even extinguish onboard fires. Point being: it’s a tough job.

2 2. They Want You To Know: They Can Perform Hand-to-Hand Combat

While it’s not mandatory on most airlines - except for Hong Kong Airlines - flight crew are encouraged to take up voluntary training, which must seriously come in handy when dealing with unruly passengers.

Considering that it's most likely relied upon when dealing with potentially violent passengers or hijacking situations, we hope we never have to see our flight attendants go Chuck Norris on anyone, but it’s certainly reassuring to know they can, if absolutely necessary.

1 1. They Want You To Know: Your Appearance Has Been Noted

The flight crew is always aware. They’re not being judgemental - it’s just part of their job. As you board, you’ll be greeted by a smiling flight attendant but they aren’t just being friendly. Flight attendants are actually assessing whether you'll be a safety concern on the flight. They're also checking you out to see whether you might be an asset in the case of an emergency, and they’ll make this assessment based on how you look. For example, if you’re physically fit, you could be a valuable resource in case of an emergency.