Which passenger gets the armrest and when is it acceptable to recline your seat? Experts give their answers in our essential guide to airplane etiquette

What is it about air travel that can turn even the most reasonable people into beings of supreme self-interest? This was best illustrated in an image that went viral last week, of a woman lounging with her trainer-clad feet propped up on the headrest of the seat in front.

Of course, the lack of space, proximity to others, and the frustration of delayed arrival or departure pose challenges to civilized behavior. But are there red lines we still shouldn't cross?

1. NO bare feet

It's bad enough to put dirty shoes on the chair. “But an equally no-no is removing socks and shoes, even if the feet remain where they should be: on the floor,” says etiquette consultant, author and former Debrett's lecturer Jo Bryant.

After all, who wants to look at horrible, gnarled trotters? Even if you keep your podiatrist on speed dial, sitting or walking around the booth barefoot is still the epitome of bad manners.

For more comfort, pack a pair of slippers or flight socks in your carry-on — “and never use the armrest as a footrest between the seats in front of you, with your toes sticking through,” says Bryant.

2. DON'T FIGHT OVER THE ARMREST

Think of it as a dividing line rather than a battlefield. The courteous response is to allow middle seat passengers to use the armrests as they are placed on the bookends by fellow travelers.

“Otherwise, you can enter carefully by just placing your elbow on it so your neighbor can do the same,” says etiquette expert and author William Hanson.

3. DO NOT PACKAGE SHARP SNACKS

The hut is not the place for sulphurous egg sandwiches, tart citrus or spicy curry salads. Choose mild choices such as chocolate, crackers or soft fruit. For easy, packable stomach fillers, protein bars are also a good choice.

4. STAY IN YOUR LANE

Never enter the designated areas of your fellow passengers. You don't have to stretch out with your feet stretched out under the seat of the person in front of you or throw sweaters over the seat behind them. Also keep the space around you – small bags, magazines and all your other in-flight essentials – as tidy as possible.

“If the person next to you falls asleep and you want to get up or he or she is slumped over, gently tap him or her. Under no circumstances should you attempt to clamber over it; you wake them up and find yourself in an embarrassing situation,” Hanson says.

5. NO PERSONAL CARE

Traveling by plane means that fellow passengers are an interested audience for your personal habits. But keep your physical care strictly to yourself.

“This is not the place to clip nails, pluck eyebrows, spray on deodorant or do anything that comes close to personal grooming,” says Bryant. If you need to prepare and prune, do it in the laundry room.

6. ALLOW DRIVERS TO CONTINUE THEIR WORK

Unless you need to answer a call of nature, you will remain in your seat while the cabin crew is performing onboard service. And be unwaveringly charming. As the saying goes, 'You win more wars with honey'.

So, says Bryant, “be patient if things move slower than you want. Smile, greet them warmly, sit down and let them do their work.” When you leave, also take the time to thank them.

7. DO NOT LOWER YOUR SEAT DURING THE MEAL

Even small children may have difficulty negotiating their food if the front seat is reclined. 'Be considerate of those behind you and do not lie back minutes after take-off. If possible, wait until after the meal and only fully recline if absolutely necessary.'

Remember that it is your prerogative to sit back, so a quick glance with a smile on the lips to check that the table top is not behind you is a polite gesture.

8. WAIT YOUR TURN BEFORE disembarking

Hitting the tarmac is not a signal to get up immediately or jump over the heads of other equally tired, bored and impatient passengers. This is not the school bell. The doors aren't even open yet. All you're doing is shoving your derriere in the faces of others who, sensibly, remain seated.

'Have others take items from the lockers and filter them out of the plane row by row. And always help those who cannot easily reach the lockers,” Hanson said. “If you're that desperate for a quick exit, pay for a seat near the front.”

9. DO NOT OVERLOAD THE OVERHEADLOCKER

Avoid unnecessarily spreading your duty-free stock in the cabin area. And don't rearrange other passengers' luggage to make room for your own.

The courteous thing you can do is to place your carry-on luggage sensibly, making the most of the overhead space, and place any other unnecessary items (and whatever you need during the flight) under the seat in front of you.

10. Whether or not to change seats

You bought and paid for your seat because you like to watch the world go by outside the airplane window. So should you trade places with someone who is separated from his or her child or partner? Frankly, it is a matter of choice and not obligation.

Just like you should think twice before asking another passenger to switch seats. “And if you do, make sure it's a fair exchange, like an aisle seat for another,” Hanson says.

11. STORY THE CHATTER

Some people like to talk to complete strangers during a flight. If you don't feel like chatting, bury your head in a book, put on headphones (even if they're not on), close your eyes, or respond monosyllabically but politely when asked a question. “Don't be afraid to say, 'I'm sorry to be so antisocial, but I'm just going to close my eyes/catch up on this book or movie,'” Hanson suggests.

…and here's what's really annoying the cabin crew – by a former British Airways flight attendant

FOLD your coat and place it in an empty upper cupboard and then close it. Believe me. That space is needed for the luggage of other passengers.

PROVERB: 'You've got to love Venice/Dubrovnik/Barcelona', or wherever we're going. Most days we don't get off the plane until we've brought a new group of passengers home. So don't rub it.

WAITING until we get to you before we ask indecisive children, “What do you want to drink?” Parents who ask in advance, tell us clearly, and then quickly walk us down the aisle are our favorites.

TO ORDER from the menu during the flight and then realize that your wallet or purse is in the overhead bin. It's a race to serve everyone as it is. Please don't delay us.

TO ASK: 'Should I make my connecting flight?' Most days we can barely remember where we're flying, let alone what time we're supposed to land.

TO GET angry when we wake you up on a night flight because we can't see your seat belt. It is a legal obligation to control turbulence. Announcements say you have to put seat belts over blankets for a reason.

TO ASK to view something from the depths of the Duty Free trolley. Then you don't buy it.

MOANTS about the meals. It wasn't us who made the salad so small. Or opt for those microscopic packs of pretzels.

STANDING before the fasten seat belt sign is turned off. We hate to pick up the PA and tell everyone to stay put – but we could get fired if we don't.

SARCASTIC comments about delays when getting off the plane. Believe me, we want to go home or to our hotel as much as you do.