Most airlines have “contract of carriage” rules governing passenger behavior, and enforcement of those rules is largely at the discretion of the flight crew. (anyaberkut/Getty Images/iStockphoto)

“Legging-gate” has died down, but in its place, a pressing question has arisen: How easy is it to get kicked off a flight?

The answer: It depends.

Every airline has a “contract of carriage,” which outlines, in fairly broad terms, the actions that could cause a passenger to be denied boarding or removed from a flight. Delta has a 51-page contract, Southwest Airlines has a 42-page contract and United has 30 rules in its contract. When passengers purchase tickets, they agree to all of these terms.

The enforcement of many of those rules, however, is largely at the discretion of the flight crew. Sara Nelson, international president of the Association of Flight Attendants-CWA, said that flight crews must be vigilant about looking for warning signs of disruptive behavior that could escalate after takeoff.

“Once you’re up in the air, you don’t have a lot of options. You can’t call for help. You can’t have someone taken away. It starts to become an issue that threatens the safety and security of the rest of the people on board,” she said.

(Erin Patrick O'Connor,Julio Negron/The Washington Post)

[United Airlines: ‘Your leggings are welcome’ — as long as you’re paying for your flight]

You can wear your leggings on the flight (as long you’re not using an employee pass on United) but there are a number of other personal choices that could get you kicked off. Here are six tips to avoid getting booted from a plane.

Don’t get intoxicated

This, Nelson said, is the first reason that someone might be turned away at the gate or get thrown off a plane. Alcohol may contribute to air rage (in fact, it was involved in a recent incident of threats against other passengers), and that’s something that the flight crew wants to avoid at all costs.

“If your flight is delayed, you might want to sip those drinks at the bar a little more slowly, because you need to understand that you could get to a point where if you’re not really in control of what’s going on, you might not get on the plane,” Nelson said.

[Air-rage incidents are on the rise. First-class sections aren’t helping.]

Show up looking healthy

No one wants a sick seatmate. If a person is visibly ill, he or she may be asked not to fly, Nelson said, whether it’s out of fear of contagion (especially if there’s a known epidemic) or safety concerns.

“If someone comes to the gate and they’re clutching their chest, sweating, showing signs of a major medical event — heart attack, stroke, anything — [the flight crew is] going to very likely be very concerned about that,” Nelson said. In some cases, she said, the crew may call paramedics to conduct an assessment. The goal is to avoid an in-flight medical incident, which could put the passenger in danger and affect everyone on board if the plane has to divert.

Behave yourself

Fighting or acting aggressive (in the gate area or onboard) is a quick ticket off the plane. That’s what happened earlier this month, when a man uttered threats over the cost of a $12 blanket.

[Two girls barred from United flight for wearing leggings]

Follow directions

No, you won’t get kicked off a plane for having your headphones in and missing the “fasten your seat belt” instructions. But Nelson said that if you’re sitting in an exit row and become obstinate toward the crew when they ask if you’re willing to assist in an emergency, that could be an issue.

Practice good personal hygiene

It sounds, well, fishy, but references to a “malodorous” condition are a part of multiple contracts of carriage. And for good reason, Nelson said: “Odors in a confined space can actually cause other people to be ill, and that would be the concern. I think this would be incredibly rare, but that is absolutely a reason that someone could be denied boarding.”

[Sure, you can wear leggings on a plane. But please don’t.]

Consider your clothing and wear shoes

Clothing and, yes, wearing shoes are also listed in the contracts of carriage. United makes mention of being “properly clothed” and Southwest calls out clothing that is “lewd, obscene, or patently offensive.” In reality, however, Nelson couldn’t think of any instances of barefoot passengers being removed from a plane, and she said that the only time she has seen clothing that raised an eyebrow was an instance involving beachwear.

“They’re not turned away, they’re coming on the plane, but we’re looking at them thinking, ‘Oh my goodness, you are going to freeze and we don’t have blankets on the plane,’ ” she said. Still, when you read about passengers running into trouble because of baggy pants (it has happened) or other wardrobe malfunctions, that rule in the contract could be the airline’s out.

One more piece of advice. When it comes to in-flight behavior, Nelson asks passengers to consider before boarding their next flight that they are part of a community.

“They didn’t just buy a seat that is flying through the clouds by themselves,” she said. “Be aware that other people matter.”

Silver is a freelance writer and author of “Frommer’s EasyGuide to Chicago.”

More from Travel:

14 ways to survive 14 hours in coach

Can’t sleep on airplanes? These products and techniques can help.

How to avoid the worst seat on the plane this summer

They aren’t just for backpackers. ‘Poshtels’ boast chic decor and the chance to be social.

Still finding kicks on Route 66