A lawyer for David Dao said the passenger is likely to sue United Airlines. Picture: Twitter/Kaylyn Davis/@kaylyn_davis

It comes as the aviation officer behind the shocking incident gave his side of the story for the first time.

NBC News obtained surveillance footage and audio that showed Dr David Dao boarding the flight to Louisville, Kentucky on April 9.

The audio revealed that when Dr Dao refused to give up his seat to make room for crew members, gate workers called airport security.

“Were they drinking, were they doing anything like that?” the dispatcher asksed in the call.

“No it’s something with an oversold, involunteer [sic] something like that,” the caller responded.

“Oh you guys overbooked the flight? This is a departing flight?” the dispatcher asked, to which the caller replied: “Yeah.”

The surveillance footage showed an aviation security car pulling up to the plane before guards boarded the aircraft. Shortly after, Dr Dao’s wife was filmed running off and on the plane.

It comes as the aviation officer who ripped Dr Dao out of his seat shared his version of events.

The officer, James Long, claimed Dr Dao was verbally and physically abusive, and flailing his arms before he lost his balance and struck his mouth on an armrest.

The Chicago Department of Aviation on Monday released the officer’s report of the incident, in response to a Freedom of Information Act request by The Associated Press.

In the report, Mr Long said he boarded the United Express flight after being called in response to a disturbance involving two people regarding a refusal to leave the aircraft.

United has said four passengers had been ordered off the aeroplane to make room for four employees to fly to Louisville, Kentucky.

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Aviation officer James Long was filmed dragging Dr David Dao off a United Airlines plane. Picture: APSource:Supplied

Mr Long said he approached Dr Dao to ask the 69-year-old physician to get off the plane. Mr Long said Dr Dao refused and “folded his arms tightly.”

Mr Long said he reached out to “hold” Dr Dao and was able to pull him away from his window seat on the aircraft and move toward the aisle.

“But suddenly the subject started flailing and fighting,” Mr Long wrote.

Dr Dao then knocked Mr Long’s hand off his arm, causing the struggling Dr Dao to fall and strike his mouth on an arm rest on the other side of the aisle, according to the report.

Mr Long said he then dragged Dr Dao because the physician refused to stand up. Mr Long said he wrote the report and gave his version of events only because he faced losing his job.

The video taken by a passenger shows lots of screaming coming from behind the seats, then Dr Dao being dragged by his arms down the aisle of the plane as the other passengers react with horror.

In a separate report released on Monday, labelled a “Hospitalisation Case Report,” the Chicago Police Department said Dr Dao was observed striking his face against an armrest as aviation officers “attempted to escort” him from the flight.

Neither report details Dr Dao’s injuries, but at a news conference days after the incident, Dr Dao’s lawyer said the doctor suffered a broken nose and a concussion, and lost two front teeth.

Mr Long said he was able to remove Dr Dao from the aeroplane. Mr Long said that once off the plane and in the walkway back to the gate, Dr Dao said he was a diabetic, but then got up off the floor and ran back onto the aircraft.

Mr Long alleges Dr Dao, while running back to the plane, said they’d have to kill him.

Mr Long and two other aviation officers were subsequently placed on leave by the aviation department.

United CEO Oscar Munoz has apologised for the shocking incident. Picture: AP Photo/Richard DrewSource:AP

The report jibes with comments that United CEO Oscar Munoz made in the aftermath of the incident, in which he called Dr Dao belligerent. Mr Munoz later offered a more emphatic mea culpa, saying: “No one should ever be mistreated this way.”

The aviation department has also profusely apologised and vowed an investigation Dr Dao’s lawyer, Thomas Demetrio, told NBC’s Today show on Monday that he intended to file a lawsuit.

The aviation department also released its use of force policy, which was sent to all officers after the incident.

It says aviation security personnel should use force only when “reasonably necessary to defend a human life, effect an arrest or control a person,” and that the force used “shall only be that which is necessary to overcome the resistance being offered by an offender and to effect lawful objectives.”