What do you regret doing on a plane? Chances are it involves a drink.

As in, drinking and working on a computer. That’s what Peter Lewis did on a recent flight from Minneapolis to New York — with disastrous results.

There was a cup of coffee next to his laptop, “and sudden turbulence that shook the plane violently,” says Lewis, a consultant based in Paola, Kan.

“The next thing I knew, the coffee had drenched my computer,” he recalls. “My lifeline to productivity was fried.”

The lesson? Liquids and laptop computers don’t mix on planes.

You regret a lot when it comes to travel

It turns out air travel is filled with regrets. For example, a recent survey found that 84 percent of air travelers wish they hadn’t switched seats with another passenger on a plane. About one-quarter of the respondents said they felt pressured — usually by a parent asking to sit next to a child. And the problem, as you might have guessed, is that the other seat is often an undesirable middle seat.

That’s what happened to Sebastian Garrido on a recent flight from Mexico City to Houston. Another passenger asked him to swap seats because he claimed to be airsick. Garrido agreed.  

“His seat was between two really heavy guys, and on the next seat was a family with four crying babies,” remembers Garrido, a marketing manager from Mexico City. “It was the worst flight ever. I was so uncomfortable, and I couldn’t sleep.”

I was curious about the other regrets travelers had, so I asked. And as I’ve already said, many of them involved drinks, or at least liquids of some kind. But not all of them. The biggest regret of all when it comes to flying may be one that is still avoidable this summer.

Your regrets and the liquids that cause them

Here are the liquid regrets that might define your next flight, and how to steer clear of them — if you want to.

Taking off your shoes and walking around the plane

Under certain circumstances, like a long flight, it’s OK to kick off your shoes so you can relax. (Just, you know, make sure you don’t have a foot odor problem.) But what if you have to visit the restroom?

“I see people walking barefoot or in socks, without fail, visiting the lavatory,” says Elizabeth Soos, founder of the Auersmont School of Etiquette and Protocol. “Consider this: the lid of the toilet is never closed, and although the aircraft toilet is not the home type but a vacuum system, some spray lands on the floor.”

Soos says passengers immediately regret using the restroom without shoes. So don’t forget your shoes, she warns.

Drinking and flying

Avantika Krishna says one of her biggest regrets was drinking alcohol on a long-haul flight from Los Angeles to Auckland. 

“I ended up seated with a college acquaintance’s family, and we decided to enjoy a couple of mimosas to celebrate our unexpected connection,” recalls Krishna, a travel advisor from New York. “Unfortunately, I couldn’t sleep at all during the 12-hour journey and arrived in New Zealand exhausted and disoriented.”

She says the alcohol combined with the plane’s dehydrating air left her feeling miserable. She now tells her clients to skip alcohol on long flights, even in business class where the options are tempting. You’ll pay for it later.

Actually, that’s not the worst of it. Sometimes, passengers combine sedatives with alcohol on a long flight, which can easily turn into an in-flight incident meriting an emergency landing and an arrest.

Not drinking and flying

The liquids cut both ways. I’ve been on a long flight where I turned down the bottle of water offered by the flight attendants, maybe because I felt like I’d had enough, or I was sleeping. But the bone-dry cabin air and the altitude can really mess things up. The Aerospace Medical Association recommends drinking about eight ounces of water for every hour you’re in the air. 

The problems don’t necessarily start in the air if you’re not drinking enough. They begin when you land and you’re in a different time zone. You’re fatigued and having trouble adjusting to the time difference. I failed to follow the eight-ounce rule on a recent flight from Doha, Qatar, to Auckland, and I ended up paying the price. I think it took me two weeks to get over jet lag.

Yet another liquid regret.

What about your other regrets?

There are more regrets, of course. Many more.

• Paying extra for more legroom. Louise Sattler, a psychologist from Los Angeles, paid more for a “premium” economy seat, but it ended up feeling a lot like regular economy. “The seats were in the back, near a leaky and smelly toilet,” she says. (Ah, more liquids.) It’s true, those extra legroom seats are sometimes no better than regular economy class seats.

• Talking to your seatmate. This one’s a biggie. It happened to Meeshka Brand, a hiking guide in the Pacific Northwest, on a recent flight. “After a long, exhausting hiking trip, I got seated next to someone who seemed friendly at first, and I didn’t mind a bit of small talk,” she says. “But after a while, I realized he had no off switch. I was wiped out from days on the trail, just wanting to rest, but he kept talking—about his job, his dog, his last vacation.” The conversation hit a lull only at the end of the flight, and Brand says she arrived at her destination even more exhausted than when she’d left. Pro tip: Headsets are a great way to say, “I can’t talk now.” (Here is our best travel guide.)

• Being unprepared. Cheryl Conner remembers a flight from New York to Salt Lake City where she forgot the basics that make her flight more comfortable — aspirin, cough drops, pain reliever. (The aspirin is important — it’s a blood thinner that can potentially prevent a clot.) Conner, a publicist from Boise, who was on a press tour, was just getting over a cold. “I ended up in an aisle seat across from — of all people — Bill Gates,” she recalls. “He was trying to sleep on that flight and I coughed the entire time.”

What will you regret when you fly this summer?

This summer will almost certainly be filled with regrets when it comes to air travel. And while they may involve a drink or a botched seat assignment, odds are it will be something broader.

See, flying is far from the pleasant experience it was a generation ago. Planes are crammed full of people. Everything costs extra. Service may be rendered with a snarl instead of a smile. 

With the price of air travel climbing, and airports more crowded than ever, you’ll probably regret flying anywhere at all. And that’s something you can still avoid.