Lawyer Thomas Demetrio(L), who is representing David Dao, the passenger who was violently dragged off an overbooked United Airlines flight, speaks as lawyer Stephen Golan (C) and Dao's daughter Crystal Dao Pepper look on during a press conference in Chicago, Illinois, the United States, on April 13, 2017. (Xinhua/Wang Ping)

CHICAGO, April 27 (Xinhua) -- A passenger, who was violently dragged off an overbooked United flight has reached a settlement with the airline, his lawyer said on Thursday.

Thomas Demetrio, a prominent Chicago attorney representing the 69-year-old David Dao, said in a news release that "the United has taken full responsibility for what happened on Fight 3411" on April 9.

He didn't disclose the sum, which should "remain confidential" as agreed by the two sides.

Dao, a Vietnamese-American doctor, was hospitalized after three aviation policemen at Chicago O'Hare International Airport was summoned aboard and dragged him from the plane to make space for four crew members on the flight bound for Louisville, Kentucky.

He suffered concussion, a broken nose and lost two front teeth, which led to an online uproar against the misconduct.

Demetrio praised United for taking "full responsibility for what happened on Flight 3411, without attempting to blame others, including the City of Chicago."

The three aviation policemen involved in the incident are employees of the City of Chicago. They have been all put on leave for investigation launched separately by the city authorities.