The days when air travelers donned suits and dresses for a flight are long gone. Now, T-shirts, shorts and sandals are considered acceptable airline attire.
But if you go too far and treat a crowded airline cabin like your own living room — or your bathroom — expect your fellow travelers to take action.
"Passenger shaming" is an online trend in which passengers and flight attendants snap photos of you being crude or nasty on a plane and post them on Facebook or Instagram.
Some offensive scenes already captured online are photos of barefoot passengers stretching their legs over adjoining seats and tray tables. Other fliers are shown napping shirtless or clipping their fingernails.
And you may not want to see the kind of stuff found in seatback pockets and strewn under seats.
Heather Poole, a 19-year veteran flight attendant and author of the book "Cruising Attitude," said the crude behavior of some passengers has made flying less pleasant.
"As long as passengers are nice, I don't care what they wear," she said. "But I do kind of hate when they take their shoes off and walk around."