A man dragged off an "overbooked" United Airlines flight in an incident which shocked the world has launched legal action against the passenger carrier.

Dr David Dao, 69, refused to give up the seat he had paid for after being asked to leave, and was dragged by his hands on his back off the parked plane, which had been bound for Louisville, Kentucky. 

He was left bloodied after the Sunday evening incident at Chicago Airport and the footage provoked international outrage, reported CBS News. 

The Dao family issued a statement expressing gratitude for the "outpouring of support".

Citing the risk of "serious prejudice" to their client, the lawyers want the airline 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 likely presages an eventual lawsuit against United for the April 9 incident. 

Dao is scheduled to hold a press conference on Thursday, his legal team said.

The airline's chief executive, Oscar Munoz, said in an interview to ABC News on Wednesday that he will not resign.

Munoz said he felt "shame and embarrassment" and vowed it would never happen again.

The airline said it is "reaching out" to customers on Flight 3411 and "offering compensation for their flights".

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

Three security officers have been placed on leave after the incident, according to the Chicago Department of Aviation. Their names have not been released, according to the report.

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

US 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.

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