The airplane cabin turned into the classic indoor, crowded, low-ventilation space you really want to avoid if you don’t want to pick up a respiratory virus like the flu—or, more relevantly today, Covid-19. If everyone’s wearing a mask and the ventilation is blowing, it is indeed difficult to get Covid-19 when you fly. Most scientists and health care workers now agree that the virus that causes Covid-19 can travel through the air, borne aloft in teeny globs of snot. Masks can stop some of them, though probably not all—but hey, nobody really knows how many you have to inhale to get sick, either. In a plane where everything’s working up to spec, the whole cabin gets an air change every two to three minutes.