Delta Passenger Loses It on Unmasked Man, Detained by FBI

A woman got violent with an older man who refused to wear his mask on a plane -- to the point she actually smacked him and spat on him ... which landed her in hot water.

This gal's name is reported to be Patricia Cornwall, and she was flying Delta on Thursday from Tampa to Atlanta -- when, at one point during the trip, she went ballistic on an old dude ... apparently because he wouldn't put on his face covering while eating and drinking.

At least ... that's what he says in this insane video, which shows Cornwall getting in his face while she stands above him, and eventually strikes him at least once.

She doesn't seem to comprehend his rationale about not having to mask up while taking in food and beverage ... only repeating her demand, until the flight crew had to get involved.

They try and restrain her and push her back to her seat, but she struggles with them -- and eventually hawks one at the man ... who tells her she's going to jail for assaulting him twice. The woman doesn't care ... mocking him in his face, even after he calls her a "Karen."

Eventually, they get her under control ... and word is, Atlanta PD was on the ground waiting for her when they landed. Reports say she was taken to a nearby ADP station, and was then handed off to the FBI. Unclear what charges, if any, she's been booked for at this point.