This summer, around 271 million people will fly on U.S. airlines. That's a lot of opportunity to contract a summer cold  or a case of COVID-19.

Fortunately, planes use highly effective HEPA filter systems that pump cleaned air throughout the cabin rapidly. The air can be completely changed every three minutes.

And in many planes, about 40% of a cabin's air goes through the HEPA filter and the rest is piped in from outside. In fact, the air in a plane is a lot safer than in a nightclub or a packed restaurant.

So how risky is it?

If someone on your flight has an infectious disease, studies show you have around a 6% chance of catching it if they're sitting within two rows of you; and a 2% chance if they're farther away.

Those risks are also dependent on how often you fly and the movement of passengers and crew in the plane and around the airport and gate.

A greater risk of infection happens if you use the airplane bathroom. Surfaces can be contaminated with microbes or you can inhale them.

Make sure to open and close bathroom doors using a sanitizing wipe, use toilet seat covers, and close the lid before flushing. Wash hands after using the bathroom.

And anyone with respiratory issues or who is immune compromised should use an N95 mask in the bathroom, and maybe throughout the airplane.