A man was forcibly removed from a United Airlines flight from Chicago to Louisville, Ky., on Sunday, after the flight was overbooked and the passenger refused to adhere to the airline's decision to randomly remove four passengers.

In a series of viral videos, the man can be seen being removed from his seat and dragged from the plane by three members of Aviation Police, a branch of local law enforcement that covers security incidents at airports.

According to The Associated Press, one of the officers in question has been placed on leave.

The airline has confirmed that the incident that occurred on Flight 3411 from Chicago to Louisville on Sunday evening was due to overbooking.

"After our team looked for volunteers, one customer refused to leave the aircraft voluntarily and law enforcement was asked to come to the gate," spokesperson Charlie Hobart told CBC News. "We apologize for the overbook situation."

Passenger Audra D. Bridges posted the original video on her Facebook page. Her husband, Tyler Bridges, said United offered $400 US and then $800 vouchers and a hotel stay for volunteers to give up their seats.

It shows the guards grabbing, then dragging the passenger down the aisle. Screaming is heard and other passengers say "Oh my god" and "Look at what you did to him."

Bridges said the airline was forcing paying customers to give up their seats so that they could be given to airline employees flying standby who needed to work a flight in Louisville on Monday.

Passenger dragged off overbooked flight2:51

According to official data, more than 40,000 paying customers were bumped off U.S. flights last year against their will, although in the vast majority of cases that happens at the gate, well before the boarding process has begun.

That figure doesn't include those who voluntarily gave up their seat on oversold flights and received an incentive.

According to the U.S. government, 434,000 passengers voluntarily gave up seats on the country's largest 12 airlines last year, including nearly 63,000 on United. The champion of overbookers was Delta Air Lines — about 130,000 passengers on Delta gave up their seats last year.

Airlines routinely oversell flights because passengers occasionally don't show up for tickets they've paid for. But they also usually offer incentives, such as cash and travel vouchers, to customers willing to get them out of a self-inflicted jam.

According to the rules, if overselling results in delays, airlines must pay passengers twice the amount of the one-way fare to their destination, up to $675 US, if they experience a delay of between one and two hours domestically, or between one and four hours internationally.

For a delay of more than two hours domestically or more than four internationally, the maximum payout doubles to up to $1,350 US.

Charlie Leocha, president and founder of the passenger rights group travelersunited.org, says the incident is a major mistake for the carrier. 

"I just don't think that the airlines have a right to drag people off of plane physically only because of their own incompetence," he said in an interview with CBC News on Monday.

Leggings United Airlines

Nearly 63,000 passengers voluntarily gave up their seats in exchange for compensation on United flights last year. (Mel Evans/Associated Press)

"They could have planned that ahead and they could have denied boarding before people were on the plane," he said. "I've never heard of this happening and I've never seen this kind of physical abuse of passengers take place before."

Leocha says airlines don't oversell as much as they used to, but they are still not good about giving customers what they are entitled to.  

"When somebody is bumped, they need to be offered different alternatives," he said. "The airlines sometimes bargain with them and sometimes they just say 'sorry, you're off the flight.' And at that point, passengers need to know their rights," Leocha said. "That's the bottom line."

In a statement that emerged well after the backlash had begun, United CEO Oscar Munoz issued a much more conciliatory statement.

"This is an upsetting event to all of us here at United. I apologize for having to re-accommodate these customers," Munoz said.

"Our team is moving with a sense of urgency to work with the authorities and conduct our own detailed review of what happened. We are also reaching out to this passenger to talk directly to him and further address and resolve this situation."

However in a letter to employees Monday evening, he pointed out that the man dragged off the plane had ignored requests by crew members to leave and became "disruptive and belligerent," making it necessary to call airport police.

"Our employees followed established procedures for dealing with situations like this," Munoz told employees. "While I deeply regret this situation arose, I also emphatically stand behind all of you, and I want to commend you for continuing to go above and beyond to ensure we fly right."
 
A statement issued by the U.S. Department of Transportation said the department "remains committed to protecting the rights of consumers and is reviewing the involuntary denied boarding of passenger(s) from United Express flight 3411 to determine whether the airline complied with the oversales rule."

"While it is legal for airlines to involuntary bump passengers from an oversold flight when there are not enough volunteers, it is the airline's responsibility to determine its own fair boarding priorities," a spokesperson said in an email. 

Canadian Transport Minister Marc Garneau declined to comment on the specific incident, but confirmed the government's plan to give airline passengers more legal protections.

"When a passenger books a flight and is then told that it's overbooked that they have certain rights, that if their baggage is damaged, that if it's lost — those are things where the passenger must have reciprocal rights with respect to the airlines," he said. "And we'll be bringing in those measures."

A new passenger bill of rights, first announced last November, will be introduced this year and come in to effect next year, Garneau said.

With files from The Associated Press