After a United Airlines flight attendant was hospitalized following an incident with an unruly passenger, union officials are renewing calls for federal action to protect the workers.

The incident happened on United Flight 476 from San Francisco to Chicago on Sunday morning.

Law enforcement removed a "disruptive customer" upon landing at Chicago's O'Hare International Airport and one flight attendant was taken to a hospital for evaluation, United Airlines said in a statement.

Corliss King, vice president of the Transport Union Workers Local 556, renewed calls for the Abusive Passenger Act, asking federal legislators and airlines to enhance consequences for passengers who behave unruly or dangerous.

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Two flight attendants stand in front of a woman carrying a child on a flight

United Airlines flight attendants confront a "disruptive customer" on a flight from San Francisco to Chicago Sunday morning.  (Twitter @PeterKondelis)

The law would put individuals who intimidate, threaten or assault airline workers on a list and prevent them from boarding commercial aircraft.

United Airlines plane

The incident happened on United Flight 476 from San Francisco to Chicago on Sunday morning. (iStock)

"Our flight attendants are the first line of defense, but we should also be protected," King said. "So we are looking for the public, federal legislators and we’re looking for our carriers to band together to protect us. We are the most vulnerable."

Video of the incident shows several flight attendants confronting a woman carrying a child. The passenger can be heard screaming, "Where is it?"

A flight attendant runs down the aisle during confrontation with passenger

A United Airlines flight attendant was taken to a nearby hospital after an incident with a customer on the plane. (Twitter @PeterKondelis)

One of the flight attendants tells the woman, "Ma'am, we are landing" and "step back" as another flight attendant is seen running toward the encounter from the front of the plane.

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It was unclear whether charges were filed in the incident. Chicago PD said the incident is under investigation by police and the FBI. 

Fox News’ Haley Chi-Sing contributed to this report.