RELATED: Never Do This on a Plane, Infectious Disease Doctor Warns. Travelers in the know will often book themselves a window seat on any flight they know they’ll be sleeping on, if only because it helps avoiding to have to get up anytime a passenger needs to get to the aisle. Others also prefer it for how comfortable it can be to snooze while resting against the body of the aircraft. But according to Linda Ferguson, a flight attendant with 24 years of experience, you should resist the urge to rest your head against the window or hull while sleeping on an airplane because it very rarely gets cleaned, she told Reader’s Digest. According to Ferguson, while windows provide plenty of views as well as a potential pillow, they also happen to catch the coughs and sneezes of passengers who sit by them. “I see plenty of people carry Lysol wipes with them that will wipe the area around their seat. If there was a backlight and they could light up a plane with all the germs, I think it would petrify everybody,” Ferguson told Reader’s Digest. “My rule of thumb, and I never get sick, is I never put my hands in my mouth or near my face.” RELATED: Never Wear These Shoes on a Plane, Flight Attendant and Pilot Warn.ae0fcc31ae342fd3a1346ebb1f342fcb Unfortunately, it’s not just the windows that provide a nasty surface for sleeping. Ferguson also warns that using your tray table as a pillow is equally disgusting. In fact, one study found them to be the single dirtiest place on a plane with 2,155 bacteria colony-forming units (CFU) per square inch—which is eight times higher than the toilet flush button in the lavatory, Forbes reported. “Those tray tables are used for all kinds of things,” says Ferguson. “During flights, I’ve seen parents changing babies on top of tray tables. I’ve seen people put their bare feet on top of tray tables.” While Ferguson says it can never hurt to bring along your own cleaning supplies, the type of flight you’re taking might provide a clue as to how dirty the cabin could be. “If you’re flying short-haul, definitely bring antibac wipes or sanitizer,” one flight attendant said on Reddit, according to The Sun. “A lot of airlines will have the crew ’turnaround’ the plane, meaning they pick up your rubbish, fold your seatbelt over, file your magazines in the seat pocket, and then welcome new passengers.” But even sanitizing the area around your seat still leaves plenty of other areas on the plane teeming with germs, including air vents, seatback pockets, lavatories, and headrests. In this case, personal hygiene can be the best way to tackle the situation. “It’s another reminder to wash our hands,” William Schaffner, MD, a professor of preventive medicine at Vanderbilt University in Nashville, told Today. RELATED: Never Do This If You’re on an Oversold Flight, Expert Warns.