Meanwhile, United remained under the spotlight as representatives of the carrier faced tough questioning at a city council hearing in Chicago, where the airline is headquartered and where the incident occurred. One officer was placed on paid leave on Tuesday.
United also announced that passengers on United Express Flight 3411 would be compensated with cash, travel credits or miles in an amount equal to the cost of their tickets.
Powell said that while he knows that the airline had to remove some passengers, he couldn't understand why the situation was not remedied before boarding. In an interview with the Courier-Journal, Powell said that during the encounter, he chose to remove his students from the plane rather than let them witness the horrific abuse.
United Vice President John Slater said he was not at liberty to say who called the aviation police, but ruled out the plane's captain.
The airline reiterated several changes detailed by Munoz on Wednesday.
Given the wide public outrage over the incident, Dao is in a strong position as he prepares to launch a legal action, lawyers who represent airlines and passengers said.
Demetrio said no one from United, including chief executive Oscar Munoz, had contacted him or the Dao family. "No, not at all", Demetrio said.
They show a bloodied Dao being dragged by his hands off a plane after he refused to give up his seat for a flight crew that needed to get to Louisville, Ky., the next day.
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.
Attorney Thomas Demetrio indicated Thursday Dr. David Dao will sue United and the city of Chicago, which employs the officers who pulled Dao off Sunday's Louisville-bound flight.
"Our U.S. airlines have failed to promote cabin safety over their profits", Patricia Friend, head of the Association of Flight Attendants, said to ABC.
Demetrio says he "probably" will file a lawsuit on Dao's behalf.
Margaret Houlihan Smith, managing director of government affairs for United, told aldermen that the airline is also conducting its own review and will publicly release its findings by the end of the month.
"I would defy anyone to suggest that there was not an unreasonable amount of force used to help Dr. Dao disembark that plane", Demetrio said in a press conference Thursday. Dao's wife managed to exit the plane intact. "We were completely horrified and shocked at what had happened to my father when we learned of the incident". She said her parents were returning home from vacation and making a connection in Chicago out of California.
A lawyer for a man dragged off a United Express flight says airlines have "bullied" passengers "for a long time".
Last August, an American Airline pilot had to intervene on a midair flight when a drunk passenger refused to sit in his seat.