Reality TV star Kris Jenner says her most embarrassing moment was when she had sex with Caitlyn Jenner, formerly known as Bruce Jenner, on an airplane.

Kris recalled her most embarrassing moment in a new video from Cosmopolitan magazine's 50th anniversay cover shoot, reports aceshowbiz.com.

"The most embarrassing moment for me was when I was with Bruce on a commercial airliner in first class. We joined the mile-high club. We felt we got away with it. We had sex in the bathroom and we came out and nobody said anything,` the 59-year-old said.

`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,` she added.