How far can airborne covid germs really spread on a plane?

The air inside a plane cabin is essentially clean — unless, of course, someone in the next seat sneezes in your direction.

That's what experts want you to know as you think about flying again as coronavirus-related restrictions on travel ease.

Even before the coronavirus pandemic, people wondered if breathing recycled air at 35,000 feet exposed a person to more germs than they'd encounter walking down the street. And now, during this historic disease outbreak, those concerns seem only to be magnified.

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Some people are already in the habit of wiping down tray tables and other surfaces in their personal seating bubble on board, and airlines are now going out of their way to make sure passengers have the supplies necessary to carry out their own cleaning routines if they choose.

But to the question about air quality: Is the air you breathe on a plane really more likely to make you sick than air on the ground?

It's complicated, according to R. Eric Jones, an associate professor and chair of the Aviation Maintenance Sciences Department at Embry-Riddle Aeronautical University.

But the short answer is: The air onboard is clean.

Related: How radically could air travel change? These questions from Delta offer some insights.

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"I would say that sitting in an aircraft cabin is probably a lot like sitting in a movie theater," Jones said. Planes, even those decades-old ones nearing the end of their working lives, are designed to have air quality on board similar to what passengers are used to on the ground.

Achieving that is done by continually drawing in air from outside the cabin, forcing it through HEPA filters to remove most particles and germs, and then pushing it out of the cabin in a matter of minutes.

Robert W. Mann, an aviation analyst based outside of New York City, agreed with Jones. "I would be less concerned about cabin air (the recirculated portion of which is cycled through HEPA filters) than the hygieneity of cabin surfaces, armrests and tray tables, and anything in the lavs, particularly," Mann said in an email. "A good wipe down between flights and occupancies would help."

According to Japanese carrier ANA, cabin air is refreshed roughly every three minutes.

So onboard air is recycled pretty regularly. It also flows through the cabin essentially from ducts in the ceiling down to vents near the floor. That means that the cabin air circulates in a way that makes it difficult for airborne germs to spread between passengers — unless your seat neighbor rudely sneezes directly onto you, or participates in some other similarly inappropriate and unsanitary behavior.

According to the International Air Transport Association (IATA), seats on many airplanes can act as physical barriers between you and the passengers seated in other rows. They're mostly tall enough, IATA officials said during a media briefing earlier this month, to prevent droplets from spreading between rows. Essentially, they act as a blocking agent similar to the plexiglass shields that many airlines and airports are installing at check-in and gate counters.

But that doesn't mean airplanes are totally germ-free either. So passengers should still take some health precautions when they're traveling.

“You’ve got people that are in highly condensed areas, that are sitting inches apart," Jones said. “Colds, flu, any virus is going to transmit in that environment, but airlines and commercial and business operators, as a result of COVID, are taking very extreme measures to try to sanitize that environment as best they possibly can."

Related: Denied boarding after a temperature check? Here are your rights.

Though he emphasized that he's not not an infectious-disease expert, Jones pointed out that the real risk of catching something on a plane seems to come from proximity to other passengers or coming into contact with a contaminated surface, not because of the quality of cabin air.

“For me, the cabin air, I’m much more comfortable with than I would be going through a TSA line. I would probably be more worried about eating at an airport restaurant," Jones said, pointing out that surfaces in the airport or bins at the TSA checkpoint may be sanitized less regularly than aircraft interiors.

Read more: Please give us your attention as we explain the safety features of your inflight briefing.

And while airlines are going to great lengths to assure passengers that they're stepping up cleaning procedures, Jones said he still worries more about surfaces on board than the air in the plane.

"I cannot speak to the cleanliness of a cabin for contact spread," he said

Mann added that cabin air quality ranks low on his list of aviation-related health concerns.

"More than air and surfaces, my concern would be the health status of passengers in close proximity. Until we all have a way of knowing and ensuring that we are all free of transmittable disease, this will probably be a concern."