American Airlines has suspended an employee after a heated confrontation over a baby's pram.
The aftermath of the row was caught on video by a fellow passenger who said a mother was hit with the pram as it was forcibly removed.
The video shows the employee saying, "Hit me! Come on, bring it on", when challenged by another male passenger.
American Airlines has apologised to the women and her family for the "pain we have caused".
The incident occurred Friday on American Airlines flight 591 bound for Dallas from San Francisco International Airport.
It follows an incident on a United Airlines plane two weeks ago when a passenger was violently removed from an overbooked flight.
Passenger Surain Adyanthaya, who posted the video to Facebook, said the employee had "violently" taken the pram from the mother, hitting her and narrowly missing her baby.
The footage shows the mother sobbing holding her baby and begging flight attendants to return her pram.
Other passengers then try and intervene.
One man demands the name of the employee involved and when a man dressed in American Airlines uniform enters the plane, the passenger tells him: "Hey, bud, you do that to me and I'll knock you flat."
The employee confronts the passenger, pointing at him and telling him to "stay out of this", before saying: "Hit me! Come on, bring it on."
Olivia Morgan, who was standing in the door to the cabin with her eight-year-old daughter when the incident occurred, told the Daily Mail the woman had been looking for a space to put the collapsible stroller.
A flight attendant had given her permission to look for a storage space as it folds up, but said she would have to check it in if there was no room.
The American Airlines website says collapsible strollers can be checked at the gate and there is no specific rule about not putting them in overhead bins.
American Airlines have started an investigation and say the video does "not reflect our values or how we care for our customers".
A spokesman said: "We have seen the video and have already started an investigation to obtain the facts. What we see on this video does not reflect our values or how we care for our customers.
"We are deeply sorry for the pain we have caused this passenger and her family and to any other customers affected by the incident. We are making sure all of her family's needs are being met while she is in our care."
The airline say they have upgraded the family to first class for the remainder of their international trip.
The airline added: "The actions of our team member captured here do not appear to reflect patience or empathy, two values necessary for customer care. In short, we are disappointed by these actions. The American team member has been removed from duty while we immediately investigate this incident."