'Sit down, Karen': Woman taken into FBI custody after mask confrontation on Delta flight

An "unruly" passenger was taken into FBI custody after an apparent argument over face masks turned ugly on a Delta flight.

The incident happened on Flight 2790 from Tampa, Florida, to Atlanta on Dec. 23.

"Situations like these are rare for the vast majority of our customers and Delta has zero tolerance for unruly behavior at our airports and aboard our aircraft," the airline said in a statement.

Video posted on Twitter by ATL Uncensored shows a woman standing over a fellow passenger, telling him to mask up while her own mask is pulled down below her chin.

"Sit down, Karen," the man retorts amid a slew of profanities, shouts and insults from both parties. He holds up a water bottle, saying he is "eating and drinking," when a flight attendant trying to defuse the situation tells the woman to put on her own mask.

The federal mask mandate requires passengers to wear face masks on airplanes when they are not eating or drinking.

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The woman says she'll put on her mask when the man puts on his.

The situation escalates after the man calls the woman a slur. She slaps him in the face. When he says it again, she appears to spit on him before being taken away.

"This disturbance led to the injury of fellow passengers and Delta employees," according to Atlanta police who took the woman into custody once the plane landed and handed her over to the FBI, which is handling the case.

The Federal Aviation Administration reported 5,779 unruly passenger incidents this year, as of Dec. 21. Nearly 72% were mask-related. More than 100 reports involved physical assaults.