It's one of the most popular seats on the plane, but now there's a warning against taking it.
If you want a couple of hours sleep during a long-haul flight, many people take the window seat in a bid to rest their heads.
But now one flight attendant has warned why you should never lean on the window.
Cabin crew member Linda Ferguson, who has worked on airlines for 24 years, has explained the window is the dirtiest part of the plane.
She told Reader's Digest it's part of the plane passengers sneeze and cough against the most.
Ferguson explained it's one of the most touched surfaces, with people's dirty hands and hair coming into contact with.
"I see plenty of people carry Lysol wipes with them that will wipe the area around their seat," she told Reader's Digest.
"If there was a blacklight and they could light up a plane with all the germs, I think it would petrify everybody.
"My rule of thumb, and I never get sick, is I never put my hands in my mouth or near my face."
She said if you want to sleep on the plane it's best to use antibacterial spray or wipes on the parts you're going to be touching.
Ferguson revealed it's not the only notoriously dirty part on the lane.
According to the cabin crew veteran, the tray tables are often dirty and rarely cleaned between flights.
A number of parents have been caught using them as changing tables for their babies or putting bare feet on them.
A former flight attendant also weighed in, writing: "If you're flying short-haul, definitely bring antibacterial wipes or sanitiser.
"A lot of airlines will have the crew 'turn around' the plane, meaning they pick up your rubbish, fold your seatbelt over, file your magazines in the seat pocket and then welcome new passengers.
"I have lost count of the amount of times I have had to tell people how disgusting it is to change their baby on the tray table or in a seat."
They suggested also cleaning the seat belt and advised against using the seat pocket in the front of your seat.
One cabin crew member said they found everything in the pockets including "Dirty tissues, sick bags, knickers, socks, finger and toenails, gum [and] half sucked sweets".