Are long flights safe for your health?

Currently, the world’s longest non-stop commercial flight takes 18 hours and 50 minutes: It connects Singapore’s Changi Airport to New York City’s John F. Kennedy Airport. But is that trek necessary? With AI-assisted flight routes, electric planes, and other tech poised to change air travel, it’s only a matter of time before long-haul flights become more efficient. And more importantly, are long flights like that safe for your health?

There are a few health risks linked to flying (aside from being swarmed by mosquitoes or breathing in dog farts), but tacking on a few more hours probably won’t have much of an impact.

“If it’s one-seventeenth of the trip, it’s not that big of a deal,” says Fanancy Anzalone, an aerospace medicine physician and past president of the Aerospace Medical Association. Still, he says, “There’s a multitude of things that you need to be concerned about when you do go on a long-haul flight.”

Cramped conditions

Sitting still in a cramped seat for hours isn’t just unpleasant—it can lead to deep vein thrombosis, when blood clots form in the legs because of poor blood flow. The longer you don’t move, the greater your risk. Worst-case scenario, the clot can break free and lodge in the lungs. Fortunately, this is rare. And you can cut down on your risk by getting up and walking around or flexing your legs.

Passengers “really need to think about getting up anywhere between three to four hours and walk around,” Anzalone says. “But by sitting on your chair and just pumping your legs—in essence pressing down on your heels and up with your toes—that little bit can make a big difference in whether somebody is going to have [deep vein thrombosis].”

Dry air and germs

So you might be out of luck if you’re seated next to someone who is already ill. However, the idea that the recirculating air on a plane abets disease transmission is a myth. “Airflow and circulation of cabin air is quite sophisticated technically, so there is usually no high risk of getting infected even if you have someone [sick] sitting two rows before,” says Jochen Hinkelbein, a professor of anesthesiology at the University of Cologne in Germany and treasurer for the European Society of Aerospace Medicine.

You should be more concerned about the tray tables, bathrooms, and other germ-gathering surfaces you’re likely to come into contact with, even though they do get wiped down after flights. “The major airlines that are flying long-haul in my experience do extremely well in making sure that the airplane is as clean … as possible,” Anzalone says. But he does recommend traveling with disinfecting wipes or sanitizer. Really, it’s best to touch as little as possible.

Radiation and air pressure

There’s not much you can do about the cosmic rays, though. Each time a passenger flies, they are exposed to a tiny amount of radiation from space. “The more time you’re on the plane, the more radiation exposure you’ll get,” says Steven Barrett, an aerospace engineer at MIT.

However, the radiation most travelers are exposed to in a given year falls comfortably within the recommended radiation exposure for a member of the public. “The very frequent travelers who are flying on long-haul flights could potentially go above the recommended limits of radiation exposure,” says Barrett, who has calculated how much radiation flyers are exposed to. “But that’s not within the region where you’d have any real health concerns.” It’s unclear how harmful these still-low levels of radiation exposure are, or if they are harmful at all, he says.

Pilots and other flight crewmembers do spend enough time in the air that the Centers for Disease Control and Prevention considers them radiation workers. The agency recommends they try to limit their time on flights that are very long, fly at high altitudes, or fly over the poles.

Another concern is that the air pressure is also lower on a plane than it is at sea level. This doesn’t bother most people. However, the thin air can cause problems for those who are old or have heart conditions or other pre-existing illnesses.

Overall risk factors

Ultimately, the longer a flight is, the more time you have for something to go wrong. And planes have become larger in recent years, which also increases the probability of in-flight medical emergencies.

“Traveling itself is becoming more and more popular, more and more convenient even for the old ones with … pre-existing diseases,” Hinkelbein says. “So we have an unhappy triad which is the setting is not ideal for unhealthy persons, the persons are older and older and having more pre-existing diseases, and not moving within the aircraft cabin, drinking only a little bit.”

For these crises, airline staff are equipped with medical kits and equipment such as defibrillators. “Every one of the long-haul flights have a way by radio to connect to physicians that are available around the world to talk to them,” Anzalone says. “I have talked to pilots about medical issues that are on board and how to handle it, do you divert or not divert.”

However, very few airlines have forms to document when passengers do get sick, Hinkelbein says. He’d like to see standardized forms and an international registry where all in-flight medical problems are reported. “Then you can try to figure out what are really the most [frequent] causes of in-flight medical problems.”

For the vast majority of people, though, even the longest flights will pass uneventfully. “The flying public on major airlines is very safe,” Anzalone says.

Plane emissions

In fact, a plane’s most profound influence probably isn’t on the passengers—it turns out that airplanes cruising miles above the Earth’s surface can cause problems down below.

“The main health impact is probably emissions that come from them and the health impacts for people for the ground,” Barrett says. He and his colleagues have estimated that 16,000 people globally die each year because of air pollution caused by planes. These emissions, which are linked to lung cancer and cardiopulmonary disease, came from planes at cruising height as well as those in the midst of takeoff and landing.