The Harlem Shake has joined the Mile High Club.

A group of Colorado College students gave flight to the dance fad by shaking their booties on a Feb. 15 Frontier Airlines trip from Colorado Springs to San Diego.

It was all in good fun — but their viral YouTube video has prompted a Federal Aviation Administration investigation into whether their costumed, sky-high dance performance violated flight safety rules.

The FAA isn’t sure what rules might have been broken. “That’s why we do investigations,” said a source.

Flight attendants gave the OK to the dance moves, and the seat belt light was off, says an account in the Colorado College student paper, The Catalyst.

Matt Zelin, one of the costumed students who staged the stunt, told the paper that a flight attendant gave him a public address mike and said, the “floor is yours.”

“The music didn’t work and nobody had the song downloaded and it was actually just people dancing around on an airplane with no music playing whatsoever,” Zelin said.

But it’s a YouTube hit, with more than 400,000 hits as of this afternoon.