Travel Etiquette: How Much Is Too Much to Drink on a Plane?

Welcome to Travel Etiquette, a new TPG column that explores the fragile social contracts and the delicate dos and don’ts of travel. Have an opinion or suggestion for a future subject? Sound off in the comments below.

At last! You've finally earned that coveted elite status, and now you get free drinks on all your complimentary upgraded flights.

Or maybe it's been one grueling business travel week, and you just can't wait to plop down in your seat and order that gin and tonic. Or three.

Many travelers enjoy having drinks on a plane — especially a welcome glass of bubbly in business class or a glass of red wine to help them relax and nod off.

And a plane can feel like the perfect spot to go slightly overboard: Nowhere to be (or at least no driving required) and not much else to do.

But drinking on an airplane, for many reasons, is simply not the same thing as ordering a drink at the local bar. In addition to your own well-being, after all, you're imbibing in a metal tube at cruising altitude, surrounded by hundreds of other people.

In fact, according to some members of the TPG Lounge, "drunk passengers" are a huge pet peeve — whether or not it's the happy-go-lucky, "singing in the aisles" drunk or the belligerent, rude and even incoherent kind.

And that's not even taking legal ramifications into consideration.

The science of drinking on planes

Contrary to popular belief, drinking on a plane doesn't make your body metabolize alcohol more quickly. This common misconception arose from sloppily-conducted research performed in the 1930s, when a Columbia University psychologist arbitrarily concluded that imbibing two to three drinks at 10,000 to 12,000 feet above sea level resulted in the equivalent loss of control experienced by someone consuming four to five drinks at sea level.

Yet a number of subsequent studies debunked that research; a 1985 Federal Aviation Administration (FAA) report found that decreased oxygen at high altitudes had more of an effect on cognitive performance than alcohol did. The FAA study results — and numerous others — are consistent with what we know about hypoxia, which is a deficiency of oxygen reaching living tissue that takes place at high altitudes or other environments where oxygen becomes scarce.

But these days, with the most modern aircraft cabins designed to more closely simulate surface-level oxygen levels and humidity, most travelers generally won't feel the side effects of altitude sickness to the same degree they would have in past decades.

Still, though airplane cabins are designed to keep your blood oxygen levels as close to normal as possible, they just aren't quite there yet. Dr. Drake Coffey, clinical instructor of emergency medicine at Harvard Medical School told TPG that "In reality, studies show up to a 4% drop in oxygen saturation at altitude, even in a pressurized cabin."

At high elevations, our bodies simply have less access to oxygen than they would at ground level. Molecules are thinner and less dense. Since our bodies already are adjusting to suddenly decreased oxygen levels, alcohol consumption at 35,000 feet can further inhibit our ability to synthesize the comparatively scarce amount of oxygen is available.

This is one of the reasons why it's actually much easier for travelers to feel and act drunk on a plane than they normally would at ground level. Another? Plane cabins still tend to be quite arid, and alcohol can exacerbate dehydration.

"We often find that people become inebriated sooner...and they're not [understanding] how alcohol will interact with [their] system with the decreased oxygen levels," Sara Nelson, international president of the Association of Flight Attendants told TPG.

And drinking on an empty stomach leads to far faster blood alcohol absorption, whether on the ground or up in the air — yet another factor that makes it easier to get drunk in-flight.

Of course, the blood alcohol absorption and effects of different drinks will vary from person to person based on a number of factors such as weight, height and sex. But the percentages, once absorbed into the bloodstream, consistently correlate to the same behavioral stages for everyone. These range from subclinical (basically normal) and "euphoria" to confusion, stupor and "coma."

Boarding rules

To determine if there's a hard-and-fast rule for how much travelers should drink on planes, we spoke to a number of air travel professionals.

"If you are inebriated, you are not permitted to board," said Nelson.

Flight attendant Amanda Pleva elaborated on this, explaining that if she can tell someone is intoxicated during the boarding process, "it's not if there will be a problem — it's when."

"Even a happy drunk," Pleva explained, "could land the crew in huge trouble with the FAA, since the law is so clear. So if you've had a few, chill out, straighten up a bit and [get] sober."

This, folks, is the big one. It's not a question of etiquette, but law. If you're drinking at the airport lounge or bar before boarding, know that it is illegal to board an aircraft when intoxicated.

Red light, green light

"All flight attendants," Nelson explained, "are required to undergo alcohol training." They're taught the very same "traffic light system" that restaurants and bars use to categorize (and keep an eye on) imbibers.

As a passenger, it can be helpful to keep this in mind. If you're in the green, you're enjoying a drink socially, are not intoxicated and are behaving (mostly) normally.

Once you move into the yellow you're displaying lower inhibitions, more amorous behavior and may be more emotional.

If you've entered the red zone, you're now posing a risk to yourself and everyone else on the plane. Your motor functions are impaired, you may feel anxiety and depression, and you're at risk for getting ill.

"It's very difficult to get to that point on a plane if you're only being served drinks," Nelson said. Passengers who drink before boarding or drink alcohol they've snuck onto the plane are far more likely to get seriously intoxicated on a flight.

Getting sick on an airplane is a miserable experience. And it's miserable for everyone near you, too. Before you drink yourself straight into the barf bag, consider the travelers who are stuck alongside you. They have fewer options than you do.

Other considerations

Even though it's not illegal to be inebriated on a flight, and there's no fixed number of drinks flight attendants are allowed to serve any given person, there are a few simple guidelines travelers can follow to make sure they're not drinking too much.

"If you're an infrequent traveler, be very conservative about how much alcohol you're drinking," Nelson urged. "And every time you have a drink, have at least as much water."

Jay Robert (also known as A Fly Guy) told TPG that travelers should remember that "one in the air is two on the ground" when drinking. "An aircraft," he added, "is not a night club."

Nelson said that flight attendants typically come by every one and a half to two hours, on average. If you want to make sure you're pacing yourself appropriately, only order a drink when a flight attendant is already passing through. "That should give you time to metabolize."

Don't think of the call button, she said, as your "vodka-tonic button." "It's a signal system — it's not intended to be for ordering drinks."

Robert agreed, saying that if you really want a drink and a flight attendant isn't around, "get up, stretch your legs and come to the galley to ask for something."

If you intend to drink on a plane, don't forget to pack ample snacks. People often miss meals during travel days, and there's no faster way to cross into the red zone than by drinking on an empty stomach.

And "for heavens sake," urged Pleva, "don't order drinks during boarding."

The bottom line

At the end of the day, drinking on a plane is a rather serious responsibility. Any health concerns that may arise, or any behavioral excess that may be triggered by drinking automatically become the problem of your fellow passengers and the flight attendants charged with keeping you all safe.

If you're obnoxious, or if you develop any medical issues that require an emergency re-route and landing, you're inconveniencing everyone else at best, and putting others in danger at the worst.

"One reason I stand at the door and engage each adult passenger in conversation is to assess if they are under the influence," Robert said. "I'm looking, listening and even smelling for signs of intoxication. Aside from being very annoying at 35,000 feet and possibly a security threat, a drunk passenger is a risk to themselves. If there is a major emergency, I need to be sure every passenger is capable of standing and running to an exit very quickly and an inebriated passenger would have a hard time doing this."

Dr. Coffey also had sound advice."Think about drinking while flying the same way you'd think about drinking while doing anything else out in public. Use common sense and your judgment. If you wouldn't walk home at night after more than two drinks, then you should probably stop at two when you're flying also. Take it slow. Check in with yourself a little more frequently when you're drinking in the sky. Get up, walk to the bathroom, see how you feel before you order another round. You might discover that you're a little more impaired than you might feel just sitting still in your seat."

Additional reporting by Melanie Lieberman.

Photo by Hutmacher/ullstein bild via Getty Images.