7:05 AM PT -- Law enforcement tells us the passenger was arrested, not the employee ... despite the passenger's claim he didn't throw the first punch.
An airline passenger and a United Airlines employee were in an all-out brawl at Newark Liberty International Airport, and the worker ended up flat on his ass.
Witnesses say the 2 began arguing before pushing, slapping and ultimately punching each other.
The video starts mid-fight ... the worker seems to push the passenger, who then slaps the employee in the face, and then all hell breaks loose.