Delta passenger slaps flight attendant on plane in disturbing incident captured on video

MIAMI (KABC) -- An airline passenger slapped a Delta Air Lines flight attendant during boarding in a disturbing incident that was captured on video.

The confrontation began with a pair of passengers refusing to buckle their seat belts and put on their face masks on a flight that was set to take off from Miami for Atlanta.

Witnesses said the flight attendant had already told the passenger to deplane for refusing to follow crew instructions, when the female passenger suddenly slapped the flight attendant across the face.

Caught on camera: Passengers brawl on plane leaving Las Vegas

A disturbing scene was caught on video on board an American Airlines plane on Monday.

A number of other passengers, some of whom are heard audibly gasping in shock, recorded the incident on their cellphones.

Security officers were called to deal with the assault and remove the two passengers, and the flight ended up being delayed more than four hours.

WATCH: 'May I recline?': Viral dispute in midair leads to debate over airline etiquette

By now, millions have watched the viral video of a confrontation in midair. A clip posted to Twitter shows a woman attempting to recline, and a man repeatedly forcing her seat forward.