In terms of the common cold, it is now well-accepted that acute respiratory infections are frequently experienced after air travel. So it's no surprise when we find ourselves getting sick after flying. Studies have found a high prevalence and wide array of respiratory viruses in people who have recently traveled.

Flying does not directly "cause" a cold, as colds are caused by viruses, but the airplane environment significantly increases your susceptibility to catching one. The primary factor is the extremely low humidity in the cabin, which often drops below 20% on long-haul flights. This dry air dehydrates the mucous membranes in your nose and throat, which are your body's first line of defense against airborne pathogens, making it easier for viruses to take hold. Furthermore, while HEPA filters in modern aircraft are exceptionally good at removing 99.9% of bacteria and viruses from the air, the high density of passengers in a confined space increases the likelihood of "surface transmission" via tray tables, armrests, and lavatory door handles. The physical stress of travel—including jet lag, disrupted sleep, and the mild hypoxia caused by cabin pressure equivalent to 8,000 feet—can also temporarily weaken your immune system. To minimize risk in 2026, travelers are advised to stay hydrated, use a saline nasal spray, and practice frequent hand hygiene or use sanitizing wipes on high-touch surfaces around their seats.