LeAnn Rimes -- Accidentally Sets Off Airplane Fire Alarm ... MY BAD!!! (VIDEO)

LeAnn Rimes is lucky she's famous ... because most people would be in serious trouble if they set off the fire alarm on an airplane, but she was able to joke about it.

The country music/reality TV star was on a flight to Los Angeles, when she took a bathroom break to freshen up. As she explains it: "Leave it up to me to set off the fire alarm in the airplane bathroom w/ @theDrybar dry shampoo #purecomedy #firsttimeforeverything."

Our photog was waiting for LeAnn when she landed, and she laughed off the whole thing -- although it sounds like the flight staff wasn't as amused ... at first, anyway.