The clip, posted to Facebook on Friday by a bystander on the flight, shows a woman in tears with a young child in her arms, and a man emerging from his seat to confront a male flight attendant.
Facebook user Surain Adyanthaya, who put the video on his page, said in his post that the flight attendant had forcefully taken the stroller from the woman, hitting her with it and just missing her child.
"You do that to me and I'll knock you flat," the unidentified man tells the flight attendant.
The crew member then points his finger angrily and challenges the passenger to hit him.
The video shows the man eventually returning to his seat.
American Airlines said in a statement it was investigating the incident, which took place before the plane took off on a flight from San Francisco to Dallas.
The woman elected to take another flight and was upgraded to first class, the airline said.
Less than two weeks ago, United Air Lines found itself in a public relations nightmare when a video appeared online showing a 69-year-old doctor being dragged off one of its flights to make room for a crew member, sparking international outrage and policy changes by the airline.
(Reporting by Barbara Goldberg in New York)
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)