Here’s the Dangerous Thing You’re Probably Forgetting to Do Before a Flight—And Why It’s Such a Big Problem

As a fresh-faced college grad, I was on a flight to Dallas for my first big job interview, and I was a wreck. Somewhere over Oklahoma, the nerves caught up with me. I started feeling hot, then nauseous, then distinctly like I was about to meet my breakfast again. I aimed the tiny air vent at my face. I tried deep breathing. I tried thinking about literally anything else. None of it worked. Reader, I used the barf bag.

It remains the only time I’ve thrown up on a plane. I’ve since learned that my midflight … ejection was caused by a surprisingly common problem for passengers, one with consequences potentially far more serious than needing to use that little paper pouch for its intended purpose. Unfortunately, many of us are so busy worrying about catastrophic what-ifs—turbulence, delays, ripped-from-the-headlines airplane disasters, whether we’ll be seated next to someone who thinks airplane armrests are a single-person amenity—that we make this surprisingly dangerous mistake.

It’s something so simple to fix that flight attendants can’t believe how often they see passengers get it wrong. “We see it all the time. Sometimes it ends up being a medical emergency when it could’ve been easily avoided,” says Loretta Hill, a JetBlue flight attendant with 10 years of experience.

So what is this overlooked danger lurking in your preflight routine? Read on to find out the step you’re overlooking, why it matters and how to stay safer next time you fly.

Get Reader’s Digest’s Read Up newsletter for more travel, tech, cleaning, humor and fun facts all week long.

What are you likely forgetting to do before your flight?

Drink water—and lots of it. Yes, really. The thing standing between you and a potential medical emergency at 30,000 feet might just be a glass (or five) of H2O. And before you roll your eyes thinking this sounds like yet another wellness lecture from that friend who carries a gallon jug everywhere, hear me out: Dehydration during air travel is a shockingly common problem, and it’s catching travelers off guard constantly.

Think about what happens when you’re getting ready to fly. You’re running around packing, stressing about whether you remembered to turn off the coffee maker, standing in security lines and sprinting through the terminal because somehow Gate B47 is always in a different time zone from the rest of the airport. Throughout all this chaos, drinking water is probably the last thing on your mind. You might even avoid drinking because you don’t want to deal with those tiny airplane bathrooms or miss your boarding call while stuck in a restroom line. (I am so guilty of this one.)

And then there’s the security checkpoint issue. “Airline travel is especially prone to dehydration, as your fluids are taken away from you while passing through airline security,” says David Cutler, MD, a board-certified family medicine physician at Providence Saint John’s Health Center in Santa Monica, California.

It’s like they want us to shrivel into dried-out husks … or be forced to buy a $10 bottle of water.

Do people get more dehydrated when flying?

Absolutely. The airplane cabin environment is basically a perfect storm for sucking the moisture right out of your body. Cabin humidity can drop below 20%, which is drier than most deserts. Your skin, your eyes and your nasal passages are all working overtime to stay moist while the recycled air does its best to turn you into human jerky.

But it’s not just the altitude working against you. Dr. Cutler explains that flying creates a uniquely dehydrating situation: “Once you’re on the airplane, which is a particularly dry environment, it may be a while before fluids become available, and even then, there may be a cost, which further hinders easy access to correct dehydration.”

So yes, there’s something about the high altitude and cabin conditions that genuinely makes dehydration worse. Combine that with the fact that you were probably already running on empty from your hectic preflight routine, and you’ve got a recipe for trouble. It’s no surprise that flight attendants prioritize hydration as one of their top strategies for staying healthy on the job, Hill says.

What can happen when you’re dehydrated on a flight?

“We’ve had people just get up and faint because they haven’t had anything to eat or drink,” Hill says, adding that falling in the cramped confines of an airline cabin adds extra risk of injury.

The symptoms of dehydration can range from mildly uncomfortable to medically serious, and they can escalate quickly. At the mild end, you might experience dry mouth, fatigue and that general foggy feeling that makes even ordering a ginger ale from the beverage cart feel like a monumental decision.

But as dehydration progresses, things get worse. Dr. Cutler explains that moderate dehydration causes “dry mouth, lack of sweating, decreased or dark-colored urine, fatigue, dizziness or lightheadedness.” These symptoms are unpleasant enough on solid ground, but in a pressurized cabin where you’re trapped for hours with nowhere to go, they become significantly more problematic.

Severe dehydration is where things get genuinely scary. “Little or no urine is made, and this can cause kidney damage. Confusion and altered mental status can cause errors in judgment resulting in significant adverse health consequences,” Dr. Cutler warns. “Rapid heart rate and rapid breathing can result in damaging heart and lung conditions. Low blood pressure can lead to passing out or eventually the state of shock where multiple organs may not be adequately perfused with circulating blood and thus damaged.”

Hill has seen her share of these in-flight emergencies. Passengers who skip eating and drinking before their flight sometimes faint, creating the kind of medical situation that can divert a flight or require an emergency landing. And as any experienced traveler knows, there are few things worse than being the reason an entire plane full of people misses their connections.

When is this more likely to be a problem?

Holiday travel is prime time for dehydration disasters—and it’s not hard to understand why. You’re stressed, you’re rushed, airports are packed, and you’re probably focused on getting to Grandma’s house rather than finding a water fountain. The period between Thanksgiving and New Year’s Day is the busiest time to fly, which means longer security lines, more gate-area chaos and less time to think about basic self-care.

Long-haul and international flights amplify the risk significantly. When you’re in the air for 10 or more hours, even mild dehydration at takeoff can become serious dehydration by landing. The longer you’re exposed to that dry cabin air without adequate fluid intake, the worse things get.

“Certain populations are at greater risk of dehydration,” Dr. Cutler notes. “This includes the very young, the elderly, pregnant women and those with underlying health conditions, which may impair the ability to recognize or correct dehydration.” Oh, and new college grads who are very anxious about their upcoming job interview. (I realized later that I hadn’t drank anything that day, and combined with my nerves, dehydration likely led to my vomiting attack.)

Delayed flights are another sneaky culprit. You’re stuck at the gate, you don’t want to leave to find water (what if they start boarding?), and before you know it, you’ve been sitting there for three extra hours without a sip. Red-eye flights pose their own challenges. You’re exhausted, might skip dinner to sleep on the plane and wake up somewhere over Nebraska feeling like you’ve been licking sandpaper.

There’s also the alcohol factor. Hill offers a pointed reminder: “The effects of alcohol are doubled in the air. Don’t take Xanax and drink!” If you’re calming your preflight nerves with a cocktail or two at the airport bar, you’re actually accelerating your dehydration while simultaneously impairing your judgment about how much water you need—not the best combination when you’re about to be sealed in a metal tube for several hours.

What should you do to prevent this?

Preventing flight-related dehydration is straightforward—you just have to make it a priority instead of an afterthought. Here’s your hydration game plan:

• Start hydrating the night before. If you have an early morning flight, treat it like you’d treat the night before a big race or event. Dr. Cutler recommends “preparing for such a situation with extra fluids beforehand.” Drink plenty of water with dinner and have a glass before bed.
• Eat before you fly. You might not realize it, but food is a significant source of hydration. Dr. Cutler points out that “food, in general, is about 75% water. So make sure you are drinking fluids if you are not eating to help prevent dehydration.” If you’re skipping the overpriced airport food, compensate by drinking more water.
• Bring an empty water bottle through security. This is the single most effective thing you can do. TSA will confiscate your liquids, but an empty, reusable bottle is perfectly fine. Fill it up at a water fountain after you clear security, and you’ll have free, unlimited hydration for your entire journey.
• Consider adding electrolytes for long flights. Plain water is great, but Dr. Cutler notes that “if drinking more than a quart of water, it is best to have some electrolytes, i.e., minerals in the water to prevent diluting out the body’s naturally occurring minerals, like sodium.” Electrolyte tablets and packets, or even a sports drink purchased in the terminal, can help you stay balanced on longer journeys.
• Don’t wait until you’re thirsty. By the time you feel thirsty, you’re already somewhat dehydrated. Sip consistently throughout your time at the airport and during the flight. Yes, this might mean more bathroom trips, but that’s actually a bonus—getting up to walk around is good for preventing blood clots.
• Go easy on the coffee and alcohol. Both are diuretics that increase fluid loss. If you need your morning coffee, balance it with extra water. And if you’re going to enjoy a preflight drink, alternate with glasses of water. Your flight attendants—and your body—will thank you.
• Set reminders if you’re forgetful. Seriously. Put “drink water” alarms on your phone for your travel day. It sounds ridiculous, but when you’re juggling boarding passes, carry-ons and all the other details of modern air travel, a little nudge can make all the difference.

Let’s be honest, your next flight will likely be uncomfortable enough without adding dehydration to the mix. So before your next trip, do yourself (and the flight crew who might otherwise have to deal with a medical emergency) a favor and drink up.

RELATED:

• Flying Out of One of These Airports? Prepare to Spend More on Parking, Beds and Booze
• Warning: You Might Get a Windowless Window Seat on These Airlines—Even if You Paid Extra for a View
• This Airline Just Made a Major Change to Its Carry-On Baggage Rules—And for Once, It’s a Win for Travelers

Why trust us

Reader’s Digest has published hundreds of travel stories that help readers explore the world safely, easily and affordably. We regularly cover topics such as the best places to visit (and the best times to visit them), tips and tricks to zoom through airport security, flight-attendant secrets, hotel-room hacks and more. We’re committed to producing high-quality content by writers with expertise and experience in their field in consultation with relevant, qualified experts. We rely on reputable primary sources, including government and professional organizations and academic institutions as well as our writers’ personal experiences where appropriate. We verify all facts and data, back them with credible sourcing, and revisit them over time to ensure they remain accurate and up to date. Read more about our team, our contributors and our editorial policies.

Sources:

• Loretta Hill, JetBlue flight attendant; phone interview, Dec. 17, 2025
• David M. Cutler, MD, board-certified family medicine physician at Providence Saint John’s Health Center; email interview, Dec. 18, 2025

Never Get Ice In Your Drink While Flying

Why Tomato Juice Tastes Better on Planes

Never Order Coffee (or Tea!) on a Plane