While in flight at 30,000 feet, passengers may exhibit certain behaviors that would be deemed inappropriate on land.

In the "r/Delta" forum on Reddit, a user titled a post "Crimes against humanity," along with a photo of a man laying back with his bare feet up on the seat in front of him.

Redditors took to the comment section to share their reactions, along with their own flying experiences.

AIRLINE PASSENGERS COULD BE REMOVED FROM FLIGHTS FOR GOING BAREFOOT: ETIQUETTE EXPERT WEIGHS IN

"This strikes me as the same type of person who would clip their nails in public," commented one user.

Another person wrote, "This is not your mom's basement, sir." Yet another Redditor said, "Living room syndrome strikes again."

Someone else commented, "This is why I travel with Clorox wipes on planes."

"Did you say anything?" asked one person. The user who posted the photo responded, "Sure did, he at least put his socks back on."

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Jacqueline Whitmore, a Florida-based etiquette expert and former flight attendant, said it is best to keep your feet covered in some capacity while on a plane.

"From an etiquette standpoint, it is rude to walk about barefoot in a public place, as many germs can be transmitted from your feet," Whitmore told Fox News Digital.

"If you plan to take off your shoes on a longer flight, it's best not to walk around without slippers for your own health and safety," she said. 

"The floor of the plane is extremely dirty, especially in the lavatory. The water on the floor is most likely not water at all."

Whitmore also said that being barefoot can impact those around you.

"For fellow passengers, seeing someone walk around barefoot can be considered unpleasant or unhygienic, which could negatively impact their flying experience."

To stay comfortable while remaining hygienic, Whitmore suggests putting on a clean pair of socks, using slippers or wearing more comfortable shoes.