A Southwest Boeing 737. Southwest Southwest Airlines has apologized to a passenger who was forcibly removed from a flight by law enforcement on Tuesday.

"We are disheartened by the way this situation unfolded and the Customer's removal by local law enforcement officers," a Southwest spokesman said in a statement on Wednesday.

"We publicly offer our apologies to this Customer for her experience and we will be contacting her directly to address her concerns.

"Southwest Airlines was built on Customer Service, and it is always our goal for all Customers to have a positive experience," the spokesman added.

In a video, filmed by a fellow traveler, a female passenger is shown being manhandled by two law enforcement officers.

The passenger pleads with the officers, telling them she had to take the flight from Baltimore to Los Angeles because her father is scheduled for surgery on Wednesday.

The passenger physically struggles with the officers before they forcibly remove her from the aircraft.

"Our Flight Crew made repeated attempts to explain the situation to the Customer, however, she refused to deplane and law enforcement became involved," the airline said.

According to Southwest, the incident took place after the passenger alerted the crew that she had what they described as a "life-threatening pet allergy." At the time, there was an emotional-support animal and a pet on the flight. The airline told Business Insider that for the passenger to continue on the flight, she needed to present a medical certificate.

"Our policy states that a Customer (without a medical certificate) may be denied boarding if they report a life-threatening allergic reaction and cannot travel safely with an animal onboard," Southwest said.

In this case, the passenger could not produce the documentation, the airline said.

The incident is reminiscent of the forcible removal of a passenger, David Dao, from an overbooked United Airlines flight in April. That incident and the widespread backlash it sparked helped initiate a national conversation about passenger treatment and the role of law enforcement in handling uncooperative passengers.

Here's the video of the Southwest incident: