Flying and physiology experts explain how long-haul flights affect our bodies—and what to do on a long flight to make your next journey more comfortable.
Here’s What a Long Flight Does To Your Body, Says an Aviation Medical Doctor
Published on Nov. 25, 2024
What is a long-haul flight?
A long-haul flight typically refers to a non-stop flight of six hours or more, according to the European Union Aviation Safety Agency. But as technology advances, a new designation has emerged: Ultra-long-haul flights. Some agencies define ultra-long-haul flights as non-stop flights lasting at least 12 hours, while others up that in-air time to at least 16 hours.
Currently, the world’s longest flight route is operated by Singapore Airlines, jetting between New York City and Singapore in 18 hours and 50 minutes. The Australian airline Qantas aims to raise the bar even higher—its “Project Sunrise” flights, due to depart out of Sydney in 2026, will have passengers in the air for up to 22 hours. This means they’ll be able to see the sunrise twice during the journey.
Yet while these airlines’ aviation experts run rigorous tests to ensure passengers’ safety, long-haul and extra-long-haul flights still can have a range of physiological effects.
How do long-distance flights affect your body?
“Altitude will have an impact on your body,” Dr. MacClements says. However, he explains there’s no difference between an airplane cabin environment traveling for a few hours versus 16 hours.
“Most airlines travel between 30[,000] to 40,000 feet,” he says, “But all commercial aircraft are pressurized to 8,000 feet.” To put that into context, there are areas in Colorado above 7,000 feet, and “up to about 40% of people will experience some degree of altitude sickness, depending on how long stay at altitude [in that area of Colorado],” Dr. MacClements explains.
So, the effects of altitude on your body in an airplane cabin can depend on how comfortable you feel at altitude in general—and, just as importantly, how long your flight is.
Still, altitude is just one way that long air flights can impact you physiologically.
You can get dehydrated
“The aircraft circulates new, fresh air regularly, but because the humidity is lower at altitude, it tends to be a lot drier than what you’re used to at sea level,” Dr. MacClements explains. “As a passenger, you might feel a little dried out.” Even mild dehydration can trigger a dull headache, and because dehydration can reduce blood flow, you might feel lightheaded and fatigued.
His first bit of advice: Skip the in-flight beer, cocktail, or coffee. “Alcohol and caffeine will dehydrate you more, and that sets you up for more discomfort.” Make sure you’re drinking plenty of water before and during your flight, he advises. “That’s why you’ll see the flight attendants coming around with water,” he explains. “Your friends on these aircraft are your flight attendants. They have been trained to make sure you’re getting the right fluid intake, the right nutrition, and the correct advice to get people up and walk around.”
Your skin can feel extra sensitive
“Long flights can have several adverse effects on the skin,” says Pooja Rambhia, MD, a board-certified and fellowship-trained dermatologist with UnionDerm in New York City. She explains that the low humidity in airplane cabins dries out your skin, disrupting its natural barrier. “This disruption can lead to increased skin sensitivity and exacerbate existing conditions like eczema, rosacea, or acne.”
“Sitting for prolonged periods and disrupted sleep further dull the skin’s appearance by reducing blood flow and slowing cell regeneration,” she adds. And—especially if you’re in a window seat—you are exposed to damaging UV rays, and they’re even stronger at altitude than when you’re on the ground.
To prep your skin against in-flight irritation, she recommends using:
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A hydrating serum with ingredients like hyaluronic acid, which helps lock in moisture.
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A rich moisturizer to create a protective barrier against the dry cabin air.
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A broad-spectrum sunscreen.
“During your flight, keep your skin hydrated by applying a non-comedogenic moisturizer or misting with a hydrating spray every few hours to counteract the dry cabin air,” she says. ” If your skin feels especially dry after the flight, it’s best to hold off on actives like retinoids or AHAs/BHAs for a couple of days to minimize the risk of irritation and give your skin a chance to rehydrate and recover fully.”
Your legs could swell
A big issue with long-distance flights is prolonged sitting because it can cause fluid to pool up in the lower legs, says Shane Davis, MD, a non-operative spots medicine doctor at Tufts Medical Center. For many people, this swelling—called dependent edema—is uncomfortable but harmless. But there are dangers of flying with swollen legs, particularly for people with any underlying cardiovascular issues. “The swelling can cause pain, but sometimes a more serious consequence in the legs during a flight is deep vein thrombosis (DVT), or a blood clot.”
Symptoms of a blood clot include cramping pain, swelling, redness, and trouble breathing. Read more about signs of a blood clot you shouldn’t ignore—and how to prevent DVT.
Dr. MacClements points to data suggesting that up to one in 10 people could be at risk for blood clot formation—particularly on longer flights with less mobility. He recommends wearing compression stockings, which help move blood flow in the veins back up toward the heart. Staying hydrated and trying to move around the cabin when possible can keep your circulation strong as well.
Still, “It is always best to consult with your physician if there are any concerns about safe flying due to underlying medical conditions,” Dr. Davis emphasizes.
You might experience gastrointestinal issues
“The gut is an organ with some of the highest amounts of nerve endings in the body, and the disturbance of the body’s natural routine—just the nature of the travel itself—can set it off,” Dr. MacClements says.
It’s called dysregulation of the gastrointestinal (GI) system, explains Dana Ellis Hunnes, PhD, MPH, RD, a senior dietitian at the Ronald Reagan UCLA Medical Center and author of Recipe for Survival: What You Can Do to Live a Healthier and More Environmentally Life. “Or, basically, jet lag of the gastrointestinal system,” she says. “Long flights typically have very dry air, and if you’re on a plane for ten to sixteen or so hours with very dry air, you get dehydrated without really noticing it, and that can dry out and harden your stools, making you constipated.” Plus, if there’s turbulence on the flight, that may force you to stay in your seat longer than you’d like—and a lack of movement can cause constipation.
“Foods on flights may be drier or not what you’re used to eating,” she adds. “Portions tend to be small and not always high in fiber, so all of these things combined can really affect your GI tract.”
Her recommendations?
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Stay as hydrated as possible.
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Bring snacks and try to eat your normal foods however you can. (You can also stay hydrated by bringing whole fruits and vegetables on the plane and getting up to move around the cabin, she says.)
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“It’s also been suggested that if you try to change your eating and sleeping timing to be more in line with where you are going, then it might help you as well to adjust,” Dr. Hunnes adds.
Your joints might ache
“The biggest effect that the airplane cabin environment has on the musculoskeletal system is the change in barometric pressure,” Dr. Davis says. “Pressure decreases at higher altitude, and the changes that occur affect gases in the synovial fluid of the joints,” which can result in joint pain—especially for people with underlying joint issues. “It’s a similar concept to how many people notice increased joint pain with changing weather.”
He says to try out items such as neck pillows, lumbar supports, compression stockings, heat or ice packs, and get in some light stretching and movement before, during, and after the flight. “Bring medications that you find helpful for your joint pain,” he adds. “If you can afford to purchase a seat with more legroom, that may be helpful—or the aisle seat will allow more freedom to get up and move.”
Your skin might break out
Experiencing acne breakouts after long-distance flights is common, largely due to the skin’s reaction to the dry, low-humidity environment in the airplane cabin, Dr. Rambhia says. “When the skin becomes dehydrated from the lack of moisture in the air, it often compensates by producing more oil, which can clog pores and trigger acne.”
The stress of travel, changes in time zones, and altered sleep patterns can also increase the body’s production of cortisol—the body’s stress hormone—which stimulates oil production and contributes to breakouts, she explains. “To help prevent breakouts, I recommend keeping skin clean and lightly moisturized before flying, avoiding heavy makeup, and using non-comedogenic products that won’t clog pores.”
You may feel nauseous
Many people get nauseated while flying, Dr. MacClements says—and the airplane cabins are actually designed to help you mitigate in-flight tummy aches. “There’s a reason why the aircraft seats tilt to 30 degrees,” he explains. When you’re tilted back at 30 degrees and looking directly forward, it’s the ideal position for your inner ear to understand and adjust to the movement, reducing the risk of nausea and dizziness associated with flying. (This trick works for motion sickness in the car, too!)
“Ginger ale really does help your stomach settle down,” he adds. But if you experience more severe nausea during flight (or GI problems post-flight), Dr. Hunnes says to speak to a gastroenterologist, as there are medications such as scopolamine patches, Zofran (a prescription anti-nausea medication,) and Miralax that may help you deal with nausea and stomach pain on a long flight.
You might feel anxious
“Some folks are just extremely anxious about flying—and that adds another level of complexity to their trip,” says Dr. MacClements. But even if you don’t typically have travel anxiety, the stress your body and mind endure on a long-haul or ultra-long-haul flight might make you feel a bit more anxious than usual.
This may be especially true if you have a mental health condition. Because the air pressure is lower in a plane cabin, your body takes in slightly less oxygen than when you’re on the ground. For many people, this can contribute to making you feel foggy or fatigued—but 2022 research published in Neuroscience & Behavioral Reviews also showed that breathing lower levels of oxygen can trigger symptoms of anxiety and depression.
If you do start to feel anxious mid-flight—or have symptoms like feeling nauseated, tingling in your fingers or lips, or your mouth feels dry—Dr. MacClements offers a few strategies to calm your mind:
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Practice meditation and focus on breathing slowly.
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Try box breathing (also called “cyclic breathing“): Breathe deeply as you count to four, hold your breath for four seconds, exhale for four seconds, and repeat.
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Do a couple of math equations in your head.
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Think about a nice, comfortable place.
You’ll probably feel a little out of it
One of the most dramatic effects of a long-haul flight is how it can take some time for your body to feel “back to normal.” Dr. MacClements says that in current research, the challenge is figuring out whether this is due to the long flight itself, the impact of altitude on our physiology, traveling across time zones—or some combination.
What is known is that just a one-hour time change—such as with daylight saving time—can substantially affect your circadian rhythm (your body’s internal clock that controls your physical, mental, and behavioral cycles). “The more you travel across time zones, the greater of an impact it is going to have on you in terms of jet lag (circadian rhythm disruption),” he says. “Your body is trying to figure out where you are, and that can have an effect on your cognitive function,” which may make you more irritable, disoriented, and impair your focus and memory. Jet lag also affects other bodily functions, including hormonal function and your gastrointestinal system.
Dr. MacClements says the best way to ease jet lag depends on which way you’re traveling:
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If you’re flying from west to east, you want to try to go to sleep at the time that you would go to sleep at your destination. (There are apps that can help you prepare for this new sleep schedule in the days leading up to your trip.)
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If you’re going east to west, the opposite is true. “You want to stay up as long as you can—until it’s bedtime at your destination.”
Does a long flight make you sick?
“There’s always a lot of anxiety around traveling in an airplane and thinking ‘Am I going to pick up the next pandemic disease?” Dr. MacClements says. “There’s always a slight risk of getting sick if you’re sitting next to somebody [with a cold or flu], but the amount of air filtration and air circulation on these aircraft absolutely minimizes the risk.”
He says that the stress of just being awake for long periods, uncomfortable, and traveling taxes your body—and the longer you travel, the more stressed your body will be. “That absolutely can make you feel a little run down,” he explains. “But once again, making sure that you eat adequately and avoid getting dehydrated can really help.”
What to do on a long flight if you have a chronic illness
Dr. MacClements notes that if you have a chronic illness, such as heart disease or diabetes, make sure that you have your medications with you in your hand luggage and plan ahead for how to take them accordingly—especially if you’re traveling across time zones. “That’s a conversation you must have with your doctor before your trip.”
In addition: Because the oxygen level decreases slightly in an airplane cabin, Dr. MacClements says people with lung conditions such as chronic obstructive pulmonary disease (COPD), severe asthma, or emphysema should see their doctor before taking a long-distance flight. “If I see [in the office] that their oxygen saturations are lower than 90%, I’d caution them about traveling a long distance and consider having them have supplemental oxygen on board.”
About the Experts
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Jonathan MacClements, MD, is a Professor in the Department of Population Health at Dell Medical School, UT Austin, a Senior Associate Dean & DIO of Graduate Medical Education, an aviation medical examiner, and instrument rated private pilot. He is also board-certified in tropical medicine and traveler’s health.
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Pooja Rambhia, MD, is a board-certified and fellowship-trained dermatologist with UnionDerm in New York City and ASDS dermatologic surgery Fellow.
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Dana Ellis Hunnes, PhD, MPH, RD, is a senior dietician at the Ronald Reagan UCLA Medical Center, Assistant Professor with the Fielding School of Public Health at UCLA, and author of Recipe for Survival: What You Can Do to Live a Healthier and More Environmentally Life.
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Shane Davis, MD, is a board-certified sports medicine physician at Tufts Medical Center, team physician for Tufts University, physiatrist, and Assistant Professor at Tufts University School of Medicine.
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SOURCES
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Jonathan MacClements, MD, a Professor in the Department of Population Health at Dell Medical School, UT Austin and an aviation medical examiner.
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Pooja Rambhia, MD, a board-certified and fellowship-trained dermatologist with UnionDerm in New York City.
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Dana Ellis Hunnes, PhD, MPH, RD, a senior dietician at the Ronald Reagan UCLA Medical Center and author of Recipe for Survival: What You Can Do to Live a Healthier and More Environmentally Life
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Shane Davis, MD, a non-operative Sports Medicine Physician at Tufts Medical Center
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Expedia: “Expedia Releases 2024 Air Travel Hacks Report for Smoother Travel”
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European Union Aviation Safety Agency: ” Operational Measures to Prevent the Spread of Coronavirus `SARS-CoV-2` Infection”
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Qantas: “A350 Project Sunrise”
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Neuroscience & Behavioral Reviews: “The interplay of hypoxic and mental stress: Implications for anxiety and depressive disorders”
