New footage of Dr David Dao, the man violently dragged from a United Airlines flight, has confirmed he refused to leave the plane out of concern for his patients.

Storyful, a company that buys social media footage, released a video on Thursday filmed by a passenger sitting behind Dr Dao.

The doctor can be heard telling the two police officers who eventually dragged him from the plane that he would rather go to jail than leave because: “I’m a physician, have to work tomorrow at 8 o’clock.”

The video also revealed that Dr Dao stood firm despite threats of violence.

One of the officers told him: “We will have to drag you … You know how this is going to end up happening, right?”

“Well, drag me then. I won’t go. I’m not going,” Dr Dao replied.

As seen in earlier videos, the 69-year-old was pulled from the seat he had paid for and dragged by his hands off the plane, which was parked at O’Hare International Airport bound for Louisville, Kentucky. He was bleeding from the mouth.

Lawyers acting for the physician have filed an emergency request with an Illinois state court to require the airline to preserve video recordings and other evidence related to the incident.

Citing the risk of “serious prejudice” to their client, 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.

The filing with the Cook County Circuit Court is a likely signal that Dr Dao will sue.

After a string of apologies, United CEO Oscar Munoz issued another statement on Wednesday saying the company would no longer use law enforcement officers to remove passengers from overbooked flights.

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

As of Thursday, Dr Dao was reportedly still recovering from his injuries in a Chicago hospital.

– with AAP