Dao's lawyers filed a petition with a Chicago court requesting that the city, which operates O'Hare International Airport, and United Airlines preserve evidence related to the incident on Sunday.
"Chicago employees should not be doing the dirty work for the Friendly Skies airline", he said.
Paul Callan, a civil and criminal trial lawyer in NY, said Dao has at least two potential claims against the airline: a personal injury claim for assault and battery, which could also target the police; and a contract claim.
"I would be shocked if there is not going to be major changes", he said.
Online video of airport security officers dragging Dao off a packed flight Sunday sparked worldwide outrage.
On Tuesday, United Airlines spokesman Jonathan Guerin said that all 70 seats on the United Express Flight 3411 were filled, but the plane was not overbooked as the airline previously reported.
It also exposed a corporate culture in which airlines - and United in particular - have long "bullied" passengers, he said.
David Dao has been released from the hospital, attorney Thomas Demetrio said at a news conference on Thursday during which a member of Dao's family spoke out for the first time. He said his client was in a "secure location" because he has been hounded by media, but that he would speak at a future date.
Demetrio said Dao had told him that being dragged down the plane aisle was more terrifying than his experience fleeing Vietnam in the 1970s.
According to Pew Research, Asians are the best-educated, highest-income racial group in the U.S. The survey reports that most Asian-Americans do not feel a sense of racial discrimination, with only one-in-five saying that they were treated unfairly or discriminated against because they are Asian.
The world has had many thoughts on the United Airlines passenger who was violently dragged off an overbooked flight earlier this week.
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The airline also said that it would no longer ask law enforcement to remove a passenger from a flight unless it is a matter of safety and security.
"United, if they're smart, will quickly and quietly settle the case", said Justin Green, a partner at the law firm Kreindler & Kreindler in NY who represents airline passengers. Munoz himself said on Wednesday that he had left a message for Dao.
But Demetrio said neither Dao nor his family had heard from United.
Chicago's Aviation Department said on Wednesday that two more officers had been placed on leave in connection with the incident.
Pepper said her father and mother had been traveling from California to Louisville, Kentucky, and had caught a connecting flight at O'Hare.
United had selected Dao and three other passengers at random for removal from the plane after unsuccessfully offering $800 in travel vouchers and a hotel stay to customers willing to give up their seats. After no one volunteered, United made a decision to choose passengers "at random" to leave.
Dao's attorney just released the following statement from Dao and his family..
But Quinn said that even without a strong case, Dao would probably walk away with a hefty settlement.
Later on Thursday afternoon, United officials reiterated their pledge to fully investigate their procedures to ensure this situation doesn't happen again. Chicago Alderman Michael Zalewski, head of the committee, called the incident a nightmare that should have been avoidable.
At least one of the officers in the videos was wearing a jacket emblazoned with the word "police", which officials banned several months ago, City Aviation Commissioner Ginger Evans told the panel.
The department's roughly 300 officers guard the city's two main airports but are not part of the regular Chicago police force, receive less training and can not carry guns inside the terminals.