David Dao launches legal action against United Airlines over forceful removal

Lawyers for the passenger dragged from a United Airlines plane in Chicago filed an emergency request with an Illinois state court on Wednesday to require the carrier to preserve video recordings and other evidence related to the incident.

Citing the risk of “serious prejudice” to their client, Dr. David Dao, the lawyers want United and the City of Chicago, which runs O’Hare International Airport, to preserve surveillance videos, cockpit voice recordings, passenger and crew lists, and other materials related to United Flight 3411.

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The filing with the Cook County Circuit Court likely presages an eventual lawsuit against United for the April 9 incident, where Dao was snatched from the seat he had paid for, and was dragged by his hands on his back off the parked plane, which had been bound for Louisville, Kentucky.

READ MORE: Video captures the argument moments before David Dao dragged off United Airlines flight

United Chief Executive Officer Oscar Munoz on Wednesday issued Dao an apology and said the company would no longer use law enforcement officers to remove passengers from overbooked flights after global outrage erupted over the way Dao had been treated by airline and airport security staff.

Munoz said United would be examining its incentive program for volunteers on overbooked planes.

WATCH: United Airlines CEO says Law enforcement will never remove passenger from overbooked plane again

0:37 United Airlines CEO: Law enforcement will never remove passenger from overbooked plane again

The Sunday evening incident caused a furor around the world as video recorded by fellow passengers showed airport security officers yanking Dr. David Dao from his seat aboard the flight.

Much of the uproar stemmed from Dao’s status as a paying passenger who was being removed to make room for additional crew members on the overbooked flight.

On Capitol Hill, powerful Republican and Democratic lawmakers denounced how Dao was treated and called for United to explain the situation.

READ MORE: United Airlines CEO says he’s not stepping down, vows to do better

On Wednesday, U.S. Senator Chris Van Hollen, a Maryland Democrat, announced plans for the Customers Not Cargo Act, which would prohibit the forcible removal of passengers already aboard an aircraft “due to overbooking or airline staff seeking to fly as passengers.”

Two online petitions calling for Munoz to step down as CEO had more than 124,000 signatures combined by Wednesday afternoon, but he told ABC that he had no plans to resign over the incident.

WATCH: Is there any legal recourse for the United passenger dragged off his flight?

3:13 Is there any legal recourse for the United passenger dragged off his flight?

Shares of United Continental closed 1.1 percent lower at $69.93. They fell as much as 4.4 percent on Tuesday.

The backlash from the incident resonated around the world, with social media users in the United States, China and Vietnam calling for boycotts of the No. 3 U.S. carrier by passenger traffic and an end to the practice of overbooking flights.

READ MORE: United Airlines didn’t bump as many passengers as these U.S. carriers last year: report

Delta Air Lines Inc CEO Ed Bastian defended overbooking as “a valid business practice” that does not require additional oversight by the government.

“It’s not a question, in my opinion, as to whether you overbook,” Bastian said on a Wednesday earnings call. “It’s how you manage an overbook situation.”

Tweet This Click to share quote on Twitter: "It's not a question, in my opinion, as to whether you overbook," Bastian said on a Wednesday earnings call. "It's how you manage an overbook situation."

As of Tuesday, Dao was still in a Chicago hospital recovering from his injuries, his lawyer said.

Footage from the incident shows Dao, bloodied and disheveled, returning to the cabin and repeating: “Just kill me. Kill me,” and “I have to go home.”

In the ABC interview, Munoz apologized profusely to Dao, his family, passengers and United customers.

“This can never, will never happen again,” he said.