Many people seem to think that if one passenger sneezes on a plane then everyone else will be sick because the air doesn’t really go out and the germs circulate in the cabin. Next time you have to fly, don’t worry about such possibility. Aircrafts recirculate up to 50 percent of the air in the cabin mixed with outside air, according to the CDC. The recirculated air passes through a series of filters 20–30 times per hour. In most newer-model airplanes, the recycled air passes through high-efficiency particulate air filters, which capture 99.9 percent of harmful particles.