Recycled cabin air and proximity to people aside, airplanes are full of disease-causing germs. Recent studies list five areas that are especially dirty: tray tables, air vents and seatbelt buckles, restrooms, seatback pockets, and aisle seats.

Tray table surfaces had 2,155 colony-forming units (CFUs) of bacteria per square inch, more than eight times the amount of bacteria per square inch on the lavatory flush buttons, an article in Time magazine reports. Two other frequently touched areas—air vent dials and seatbelt buckles—had 285 CFUs per square inch and 230 CFUs per square inch. respectively. Although airplane restrooms are cleaned frequently, they’re still an easy place to pick up infections, along with seatback pockets, where passengers have been known to stuff trash, dirty tissues and used diapers. The tops of aisle seats are held onto for support by people walking by, many coming from the restroom.