GROSS!

Leave it to Kris Jenner to make our jaws drop! In her latest interview for Cosmopolitan's 50th anniversary issue, the 59-year-old reality star admitted that she and then-husband Bruce Jenner (now known as Caitlyn Jenner) got wet and wild on a plane ride.

Kris admitted, "The most embarrassing moment for me was when I was with [Caitlyn] on a commercial airliner in first class," she told the magazine. "We joined the Mile High Club and we felt we got away with it."

"We had sex in the bathroom and we came out and nobody said anything. At the end of the flight, the flight attendant got on the microphone. 'Congratulations, Mr. and Mrs. Jenner! You've just joined the Mile High Club. We're so proud of you, and we decided to give you a bottle of champagne! Yay!' I could not squish down in my seat low enough. I was mortified!"

Well you should be mortified -- but clearly not mortified enough to keep that fun trip down memory lane quiet!

Kris appears on the magazine's 50th anniversary cover, along with her five daughters.