What do long flights do to our bodies?
From dehydration and muscle soreness to nausea and indigestion, the typical discomfort and pain can all be explained by unnatural conditions on long flights.
If you’ve taken a long flight in a seat with limited recline recently, 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 dry air that can make your throat, nose, and skin feel dry, and air pressure changes while ascending and descending that can affect your sinuses. Worst case, flying could become deadly if a blood clot forms in your extremities and moves to your lungs.
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 how your body reacts to long flight times, and what you can do to mitigate discomfort.
Dry air and changes in air pressure
About 50 percent of the air circulating in-flight is pulled in from outside the plane at high and dry altitudes—so 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 to keep you more comfortable and improve your circulation, too.
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And while some respiratory conditions like asthma can be exacerbated by cold, dry air, 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 and can result in pain in the nose and ears for some people, says Laleh Gharahbaghian, 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 also renewed 20-30 times an hour.
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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.
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
By sitting for too long, your digestive system is also affected, Lees says, as the movement of food slows on its way through the intestines.
“If you are sedentary, you do not get the physical stimulation to the intestines,” says 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.”
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A slumped posture can restrict movement of the ribs, leading to slower and shallower breathing, too, Lees says. “Shallow breathing can lead to decreased oxygen intake…This can cause foggy thinking, dizziness, and even fatigue.”
Gastric reflux can result from a slumped posture, too, and has the potential to cause nausea, says Lees.
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.
DVT and blood clots on planes
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 remain for too long in a restricted position.
“The worst thing is deep venous 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.”
Signs of DVT 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 after a trans-Atlantic 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, taking birth control, says Manyak.
Getting up to walk the aisles every hour or so during a flight, doing heel raises while at your seat and wearing compression socks, which improve circulation in the legs, are a few of the things you can do to keep blood from pooling in your lower extremities on long flights, Manyak says.
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.
