Doctor files court papers demanding United Airlines 'protects evidence'

Dr Dao was dragged from the plane Credit: @JayseDavid

The United Airlines passenger who was filmed as airport police forcibly dragged him off the plane has filed court papers demanding the airline "protects evidence" of the incident - indicating plans for future legal action.

Dr David Dao filed an emergency "bill of discovery" against United in Illinois State Court, demanding all CCTV footage, cockpit voice recordings, passenger and crew lists and incident reports be "preserved and protected".

He "currently has no access to them and believes that serious prejudice" would befall his case if the items were not safeguarded, the court papers state.

Images of the 69-year-old doctor being violently wrestled from his seat and dragged along the plane gangway have prompted outrage around the world, and turned into a PR nightmare for United.

Dr Dao was one of four people randomly selected to get off the Chicago-to-Louisville flight to make way for crew members United wanted to fly instead.

When he refused, reportedly saying he had patients he needed to see in the morning, United sent in Chicago Aviation Police officers to remove him from his seat.

Other passengers filmed as the officers grabbed him and a tussle broke out. The videos quickly spread on social media.

Initially, United chief executive Oscar Munoz apologised for having to "reaccommodate" passengers, but did not address the violence caught on camera. An internal memo seen by NBC News also appeared to lay the blame on the "disruptive and belligerent" Dr Dao.

But following days of sustained anger and an almost $1 billion plunge in the company's share prices, he issued a third statement offering his "deepest apologies", and saying it was "never too late to do the right thing".

All passengers on the flight will now be offered compensation amounting to to the full cost of their ticket, which they can claim in the form of cash, travel credits or miles.

And the Chicago Department of Aviation said three of the officers involved in the incident have been placed on administrative leave.