There are two places where you consistently have to remind people to play nice with others, stop screaming, and keep their hands to themselves. One is preschool. The other is an airplane.

It's not news that the general standard of behavior on airplanes has declined in recent years. In fact, there's a whole social media campaign devoted to it. Passenger Shaming, started by former flight attendant Shawn Kathleen, aims to shine a light on the grossest, rudest, and jerkiest behavior on airplanes by posting photos of these airborne offenders for the world to see. The goal: to end bad airplane behavior forever.

"I want to bring the [shameful] behavior to the attention of people who may not think it's an issue until they see someone else doing it and they see the response it gets [on my site]," Shawn Kathleen tells Yahoo Travel. "Maybe you'll see Passenger Shaming and say, 'Oh, s---, I do that; it never crossed my mind that I shouldn't clip my toenails on an airplane.'"

Sure, some people may bristle at the public social media shaming of unsuspecting air passengers. But the thing is, it's really easy to keep from getting passenger-shamed: Don't do anything shameful.

So if you want to up your passenger-etiquette game — or at the very least, avoid being made fun of on social media — here are some things you can do to keep from being passenger-shamed.

1. Keep your shoes on

(Ms. Shawn Kathleen)

The most frequent offenders, by far, who end up on Passenger Shaming are those who get a little too footloose and fancy free among their fellow passengers.

"You can't go into a restaurant with bare feet," Shawn Kathleen says. "It's gross." Nationally recognized etiquette expert Diane Gottsman, owner of The Protocol School of Texas, agrees. "That's my pet peeve," she says of barefoot fliers. "You are not in your living room."

Seriously, people: Keep your shoes on. Or at least, don't go barefoot. Not only is it often unsightly, but also no one wants to smell your feet — especially when we're packed 300-people deep in a contained cylinder with recirculated air.

2. Keep your feet to yourself

(Ms. Shawn Kathleen)

Not only are people going barefoot, but they're putting their bare feet wherever they darn well please. Passenger Shaming recently posted a picture of a young man posing for a selfie as the bare feet of the woman behind him brazenly perches on his armrest.

"Oh, my God — come on!" Shawn Kathleen says (seriously, she hates bare feet).  "This guy can't turn his head to the window without her nasty feet in his face." Keep your feet covered and on the floor.

3. Clean up after yourselves

(Ms. Shawn Kathleen)

You may think of leaving your trash, magazines — along with used diapers, maxi pads, and other materials too gross to mention — behind on the plane. "It's just disrespectful," Gottsman says. If you need to, think about the poor person who's got to clean that up behind you. They used to say to us during Boy Scout camping trips: "Leave the campground cleaner than you found it." Same rule goes for airplanes.

4. No PDA

(Ms. Shawn Kathleen)

We're not going to pass judgment either way on aspiring members of "The Mile High Club"; what you and another consenting adult do in the privacy of an airborne, 3x3 bathroom is your own business. But for gosh's sakes, no PDA in your seat. "If you wouldn't do it in front of your boss, you really shouldn't do it in front of other passengers," says Gottsman. If you find that the urge to get amorous with your travel companion is too strong to ignore, try reading the emergency safety pamphlet: If that doesn't kill your mood, nothing will.

5. Keep your baby out of the aisle

(Ms. Shawn Kathleen)

Believe it or not, this is a thing now. Featured on Passenger Shaming is a pic of a baby whose parents apparently thought it was okay to leave the little one right in the middle of the aisle. An anonymous flight attendant confessed to us that she saw someone else do the same thing on one of her flights.

"It's not safe," says Gottsman, noting that it blocks passengers who may be trying to go to the bathroom or, worse, flight attendants, whose primary job is to ensure our safety.

We know they may not say this explicitly in "What to Expect When You're Expecting," so we'll say it plainly: Don't put your babies in the aisle of an airplane.

6. Save the pushups for the gym

(Ms. Shawn Kathleen)

A good stretch is beneficial and often necessary during air travel. But doing pushups — which qualifies as a full-fledged workout — is a no-no. Not only does it take up much-needed space, it makes you look like a showoff. "I think doing pushups on a plane is just a form of boasting," says Gottsman.

7. Dress well (but we'll settle for just dressing)

(Ms. Shawn Kathleen)

In the past, we've taken a clear position on the need for passengers to dress better on flights. But seeing the various states of undress that pass as clothing on Passenger Shaming, we're now happy if people just simply opt to dress for flights.

"You might be comfortable, but you're still in a public place," advises Gottsman. "You don't have to dress up in a suit, but you do have to be clean, bathed." And you definitely don't want to stand out in a way that lands you on Passenger Shaming.

8. Hands off the merchandise

(Ms. Shawn Kathleen)

Please don't undo your pants and put your hands down below while flying. Do we really need to say that? Yes, apparently we do because... just look. We can't even...

9. Don't be a jerk

(Ms. Shawn Kathleen)

There's a reason why all those viral videos of people getting arrested for acting up on a plane always end with the other passengers bursting into applause: People may hate jerks on the ground, but we despite them in the air. When we fly, we're all in the same miserable boat. We all got groped by TSA, we all got gouged by high fees, and we're all smelling the stinky feet from the passenger in seat 12D who failed to heed Rules #1 and #2. So no one wants to hear your tantrum. Be nice, be easygoing, and we'll all get through this flight.

10. Remember the Golden Rule

(Ms. Shawn Kathleen)

If you can't remember any of the other rules, just remembering this one will keep you out of Passenger Shaming hell. "It's cliché, but it really is about doing unto others as you would have them do unto you," says Gottsman. It's a lesson we all learned in preschool. We should take it with us when we fly.

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