By Mike Pomranz
Updated September 09, 2015
© Patti McConville / Alamy Stock Photo

Traveling can be not just a stressful endeavor, but a filthy one as well.

But just how dirty are airplanes? And what are the most germ-ridden areas? Trip planning site Travel Math decided to get to the bottom of these questions and sent a microbiologist to take samples from four different flights.

First, the bad but somewhat expected news: Airplanes are dirtier than the average home. The worse news: Of the four places on a plane Travel Math tested, the tray table—that thing where you rest your food and, when you really can’t get comfortable, your head—was the filthiest, with 2,155 colony forming units of bacteria (CFU) per square inch. That’s nearly eight times worse than the lavatory flush button, which registered just 265 CFU per square inch. Both the seatbelt buckle and the overhead air vent also landed in the 200 range. By comparison, they say your home toilet seat is around 172 CFU per square inch. Yup, that means putting your head on the tray table is like giving yourself about a dozen swirlies.

One piece of good news: None of the samples returned any fecal coliforms such as E. coli.

Travel Math speculates that bathrooms tend to be cleaner because they get the most attention. Meanwhile, with airlines putting even more pressure on staff to turn around flights quickly, tray tables often get neglected until the end of the day because there just isn’t enough time.

The moral: If you decide to eat on a plane, maybe take your meal to the bathroom. You can see the rest of their study below.