"For a long time airlines, United in particular, have bullied us", Thomas Demetrio told reporters at a press conference in Chicago.
Video of the Kentucky physician being pulled from his seat after he refused to leave the full plane has been viewed by people around the world.
The airline has offered multiple excuses and apologies regarding the incident, saying they had asked four volunteers to give up their seats on the plane to make way for four United employees who needed to make it to Louisville to work another flight.
Crystal Pepper says seeing her father removed from the Sunday flight was "exacerbated" by the fact it was caught on video and widely distributed.
While Dao continues to recover in a Chicago hospital, lawyers representing him filed a petition with an Illinois State court demanding the airline and the City of Chicago to preserve all surveillance videos, cockpit voice recordings, passenger and crew lists related to the flight, BBC reported. The incident became a public-relations disaster for the airline company.
His lawyers filed an emergency request with an IL state court on Wednesday to require United Continental Holdings Inc and the City of Chicago to preserve video recordings and other evidence related to Sunday's incident, a likely precursor to a lawsuit.
"That is not who our family at United is", he said.
The airline said it is "reaching out" to customers on Flight 3411 and "offering compensation for their flights".
Callan said he had reviewed United's so-called contract of carriage, the fine print that passengers agree to when they buy tickets.
But when asked by ABC whether the passenger was at fault in any way, Munoz replied, "No, he can't be".
Likewise, Chicago's aviation department has said only that one of its employees who removed Mr Dao did not follow proper procedures and has been placed on leave. Two complied, while Dao, a doctor who said he had to make it to Louisville to see patients the next morning, refused.
Those documents are often the first steps toward a lawsuit.
According to the documents, the case is scheduled to be heard in the Cook County Circuit Court on August 10.
The video showing Dao, who is now hospitalized after the incident, being pulled out of his seat and screaming as officers dragged him down the aircraft at Chicago O'Hare airport, received millions of views.
Chicago's Aviation Department said on Wednesday that two more officers had been placed on leave in connection with the incident. The officers aren't part of the city's regular police force, get less training and can't carry firearms inside the airport grounds.