What do long flights do to our bodies?
From dehydration to indigestion, here are the health risks of long-haul flights—and how to survive them.
Long-haul flights can do a number on your body. If you’ve taken one recently, especially in a seat with limited recline, the discomfort of the experience is likely still painfully fresh.
While airline seat size and pitch (aka legroom) have shrunk since the 1990s, time passengers spend in the air is noticeably increasing.
When Qantas launches its nonstop Sydney-to-London route in late 2025, it will be the longest flight in the world at 20 hours of flying time. Current honors go to Singapore Airlines’ New York-to-Singapore route, which clocks in at over 18 hours.
The discomfort of long flights goes beyond cramped positions. There’s also cabin air that can make your throat, nose, and skin feel dry, and air pressure changes that can affect your sinuses.
Worst case, flying could become deadly if a blood clot forms in your extremities and moves to your lungs, a life-threatening event called a pulmonary embolism.
But experts say most of us don’t have to worry. “Generally, flying is safe for everybody and the problems only occur when you have an underlying condition,” says Explorers Club fellow Michael J. Manyak, a physician specializing in urology and expedition medicine.
Experts break down the health risks of long haul flights, and what you can do to mitigate discomfort across time zones.
Long-haul flights and dryness
About 50 percent of cabin air is pulled from outside the plane at dry and high altitudes. As a result, it’s generally far less humid than what you’re used to breathing on the ground, Manyak says. This environment can cause your eyes, nose, and mouth to feel excessively dry.
“Your mucosal areas are drying out,” he says. “The dry air contributes to a lack of lubrication in your body’s systems.” Drinking plenty of water before and during your flight will help keep you more comfortable and improve circulation.
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Additionally, while cold, dry air can exacerbate some respiratory conditions like asthma, most people don’t have to worry about symptoms beyond discomfort, Manyak adds.
Air pressure changes during take off and landing cause air in the sinuses to change. Those changes can cause pain in the nose and ears for some people, says Laleh Gharahbaghian, a physician and clinical professor of emergency medicine at Stanford University.
“This is true for those experiencing sinus disease most profoundly, and felt only mildly as ‘ears needing to pop’ for healthy folks,” she says.
Gharahbaghian recommends taking decongestants before your flight, drinking water, and taking anti-inflammatory medicine if you have a cold or congestion.
Speaking of colds—while it might feel like you get sick or catch a cold every time you fly, Manyak says airports, “where everyone is mingling in waiting areas and there are no air filters,” are more likely where the real exposure occurs. According to the IATA, air in the cabin is half HEPA filtered, half fresh from outside the plane, and renewed 20-30 times an hour.
(How clean is the air on planes?)
Muscle soreness
If you don’t get the opportunity to move around, you’re holding a position—that means prolonged engagement of your muscles, which leads to soreness.
Gharahbaghian says it’s not unusual for people to feel stiffness in their back, neck, or even their thighs while enduring the same position for a long period of time.
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Getting up to walk up and down the aisle when it’s safe or even adjusting your body and doing things like heel raises while seated can help, she says.
Most injuries can feel worse after sitting for a long period, since inflammation can build without movement to flush it out, says Kevin Lees, director of chiropractic operations at The Joint Chiropractic.
Back injuries are no different, of course, and prolonged flexion (sitting for hours) can create pressure on the disks, rubbery cushions between the vertebrae of your spine—especially your lower back.
Slowed digestion, difficulty breathing
Sitting too long also affects the digestive system, says Lees. Doing so slows the movement of food on its way through the intestines.
“If you are sedentary, you do not get the physical stimulation to the intestines,” adds Manyak. “This is one of the reasons why we try to get patients up and walking soon after surgery. It is also good for circulation and wound healing.”
Gastric reflux can result from a slumped posture and has the potential to cause nausea, says Lees.
(How exercise can help—or hurt—your digestion)
Manyak says any potential nausea or motion sickness from turbulence tends to be short-lived, since pilots try to divert from turbulent areas as soon as possible. “Motion sickness goes away almost immediately with stabilization of the environment,” he says.
Besides digestive issues, slumped posture can restrict movement of the ribs, leading to slower and shallower breathing as well. “Shallow breathing can lead to decreased oxygen intake,” says Lees. “This can cause foggy thinking, dizziness, and even fatigue.”
(Jet lag doesn’t have to ruin your trip. Here’s what you can do.)
Deep vein thrombosis and blood clots
By far, the biggest risk to your body on a long-haul flight is something that can also affect you on the ground when you’re in a restricted position for too long.
“The worst thing is deep [vein] thrombosis (DVT), or getting a blood clot in the legs,” Gharahbaghian says. “If a blood clot goes from your legs to your lungs, it can become a life-threatening problem.”
DVT symptoms include swelling, throbbing, or pain in one leg, says Manyak. “The pain occurs because you have impeded the blood supply and its return to the heart … The veins involved swell, causing pain.”
There’s a litany of factors that could predispose fliers to DVT, says Manyak, who himself learned he had a hereditary blood-clotting disorder after experiencing a clot from an international flight.
These factors include a family history of blood clots, being pregnant or having recently given birth, having cancer or undergoing active or recent cancer treatment, and taking birth control, says Manyak. Heart disease is also a risk factor, according to the American Heart Association.
Getting up to walk the aisles every hour or so during a flight and doing heel raises while at your seat can help improve blood flow, says Manyak. Compression socks can improve circulation in the legs, helping to keep blood from pooling in your lower extremities on long flights, he adds.
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It’s good advice for anybody who feels stir-crazy just thinking about their next long-haul flight. “The biggest thing that causes discomfort for travelers during a long-haul flight is the fact that you’re not moving,” Manyak says.
