"He said, 'I don't want to see your panties or anything but do you have any on?'" Knowles recalled yesterday.
"I didn't want to show him anything. He wanted me to basically show him my crotch. I was completely humiliated. It was vulgar. It was macho. It was rude."
She said fellow passengers on the July 13, 2010, flight to West Palm Beach watched in horror as she was confronted.
The former fashion model said she was wearing a baggy blue T-shirt over a pair of dark denim short-shorts she had tossed on after waking up at 4 a.m.
Knowles said she was escorted off the plane at LaGuardia Airport.
She was taken to a hangar, where she lifted up her T-shirt to prove she met the dress code.
"'Oh, she's wearing shorts,'" the JetBlue fashion police responded, according to Knowles.
"It was really crazy," she said. "I've never had a corporate employee ask me about my underwear."
Her lawyer, Brian Dratch, is seeking unspecified damages in the civil claim that accuses the airline worker of assault and battery and intentional infliction of emotional distress.
"This caused plaintiff great embarrassment and humiliation to be expelled from the flight for no reason at all in front of a fully booked flight," Dratch said in the suit.
A JetBlue spokeswoman declined to comment.
After showing off her shorts, Knowles returned to the plane, but was told by the same walkie-talkie-wielding supervisor that the pilot would not take off with her aboard.
"He said, 'The captain is refusing to fly you today. We need to remove you from the flight,'" said Knowles, quoting the supervisor. "We need to remove you from the flight."
As passengers grew upset and grumbled about the delay, Knowles acquiesced.
She was delayed four hours and put on a later JetBlue flight to Florida,where she had a business meeting.
"'You should get a lawyer,'" a fellow passenger told her as she walked off the plane.
"I really feel like the guy just wanted to demean me in some way," she said. "Maybe he thought I was cute. Even so, it was totally inappropriate."