It’s an unspoken rule of sex workers in the skies: If you’re on an airplane, you’re going to take a topless bathroom selfie.

“It’s like this badge of honor among creators,” says porn star Rachel Steele, who has participated in the trend many times. “If you’ve taken a topless plane pic, you’re part of the club.”

No, not the Mile High Club. The Topless Plane Bathroom Selfie Club is the sexy aviation alliance that matters now. Just take a quick look at Reddit, which is floodedwith amateurairplane lavatoryflashers.

The preferred selfie pose is nothing too elaborate: One hand holds the phone, the other the shirt. Sure, there are all kinds of sexier things you could get up to when the seatbelt sign is turned off, but this isn’t about crazy kinky aeronautics; the simple act itself is taboo enough.

“Part of the appeal is just how wrong it feels,” Steele tells me. “You’re crammed into this tiny little bathroom at 35,000 feet, people are sitting just outside the door, and you’re in there snapping a topless pic like it’s no big deal.”

“Airplane bathrooms are cramped, semi-private spaces where the possibility of getting caught, such as forgetting to lock the door, spikes adrenaline,” adds porn star Cory Chase, who also loves taking topless plane bathroom selfies. “That danger, paired with the taboo of doing something ‘naughty’ in a place meant for mundane necessity, taps into exhibitionist fantasies.”

Of course, this desire for “sneaky sex,” as Chase puts it, is nothing new. “When we engage in risky behavior, our bodies get a burst of the hormone adrenaline, which increases rates of circulation (gets your blood pumping — also associated with erectile function), respiration (heavy breathing) and preps your muscles for exertion,” explains Lisa Finn, a sex educator at Babeland. “These are responses that we get from and correlate with arousal as well, so when you put the two together, the feeling can be intense, intoxicating and orgasmic.”

As for how a subreddit like r/AirplaneNudes can boast some 85,000 subscribers, Finn says it represents a kind of elevated (quite literally) voyeurism. “It can be hot to see a porn star outside of a bedroom environment because it pushes the idea of reality into the narrative,” Finn says. “It feels almost like you’re peeking into their personal life.”

To Steele, it’s also a practical content win — she gets to continue posting nudes while she travels, but with a twist. “It’s not just another bedroom selfie,” she notes. “It’s travel, it’s lifestyle and it’s a little rebellious; fans love it because it feels spontaneous and daring.”

There are some other unexpected pluses, too. “The lighting in those plane bathrooms is weirdly flattering sometimes,” says Cherie DeVille, like Steele a well-known MILF in the adult industry. “It’s the closest we get to a ring light in coach.”

Not to mention, both Steele and Chase say a cute tit pic in a tiny windowless box can be a much-needed distraction during a long, monotonous ride on airplane mode. Or, as Chase tells me, “Boredom lowers my inhibitions.”

“After hours in that middle seat, you just need to stretch and remind yourself you’re a bad bitch,” DeVille adds. “Even if it’s next to a tiny trash chute and a ‘lavatory occupied’ sign.”