At a City Council hearing Thursday, Alderman Mike Zalewski, 22nd Ward, said "there are no excuses" for what occurred after Dr. David Dao refused to give up his seat Sunday.
Attorneys for the family plan litigation against United Airlines, as city officials directed United Executives and Chicago Aviation officers to appear at a special hearing at City Hall.
"All of this was totally avoidable. From the pre-boarding to the on plane procedures, to the actions by the Department of Aviation employees. There are no excuses," Alderman Zalewski said.
"What transpired from there was a very disturbing moment. We will pledge to never happen again. It was a failure of our system," John Slater, United Airlines, VP of Operations, said.
Alderman Ed Burke shared video of the incident and another incident of a passenger being removed with the Aviation Committee and shared concern that Chicago may be pulled into litigation for the O'Hare incident.
During the hearing, it was said that aviation security officers have limited authority at O'Hare but at an incident like Sunday, both aviation officials and Chicago police should respond. In this incident, the aviation security officers were the ones who arrived first, CPD officers arrived later.
While there as heated questioning, there were also apologies given by United executives.
"We are deeply sorry this occurred to Dr. Dao. We apologize to him and to the customers that witnessed this appalling scene," Margaret Houlihan Smith, United Airlines, said.
Three Aviation Security Officers have been put on paid leave from their employer, the City's Department of Aviation. But the aviation commissioner stopped short of an apology.
"Chicago employees should not be doing the dirty work for the 'friendly skies' airline," Alderman Ed Burke, 14th Ward, said.
"Why did it take an incident with United for us to have you here and then not get complete answers?" Alderman Brendan Reilly, 42nd Ward, said.
After two hours of questioning, aldermen were still looking for many answers.
"There really is no clear policy about how this is handled by the aviation security officers, and we need to get that fixed," Alderman Zalewski said,
"It was necessary for us to come out and apologize and address the issues with the committee," Slater said.
A Chicago attorney for the man who was violently dragged off an United Airlines flight at O'Hare International Airport Sunday said his client told him the experience was more horrifying than leaving Vietnam.
Dr. David Dao's daughter, Crystal Dao Pepper, joined his attorneys for a Thursday morning press conference at the Union League Club in Chicago's Loop. She said this has been a very difficult time for the family and thanked their supporters.
"We were completely horrified and shocked at what had happened to my father when we learned of the incident. Seeing it on video made those emotions exacerbated," Pepper said.
Neither Pepper, nor Dao's lawyers, have received an apology from United.
READ MORE: United Airlines Doctor Video - Moment-by-moment timeline of Flight 3411
Dao, 69, hired powerful Chicago attorneys. Thomas A. Demetrio, co-founder of Corboy & Demetrio, and Stephen L. Golan, managing partner of Golan Christie Taglia, are representing him.
Dao will need reconstructive surgery, Demetrio said. He suffered a "significant concussion," a broken nose and lost two front teeth, Demetrio said. He was discharged from the hospital late Wednesday night.
Video of the incident shows Dao got back on the plane after he was removed. Demetrio said his client was so concussed, he does not remember doing so.
When asked whether there would be a lawsuit, Demetrio responded, "Yeah, probably."
They are currently gathering all the information needed to file it. On Wednesday, Dao's lawyers asked United and the city to preserve any video or audio files from Flight 3411.
The videos other passengers posted to social media caused international outrage this week. 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. Demetrio said Dao's wife was also on the plane.
RAW VIDEO: UNITED PASSENGER DRAGGED OFF FLIGHT AT O'HARE
Demetrio said for a long time, airlines have bullied passengers. He said the future lawsuit will be in the pursuit of fairness, respect and dignity for all people who fly.
"Here's the law. Real simple. If you're going to eject a passenger, under no circumstances can it be done with unreasonable force or violence. That's the law," Demetrio said. When they're ready, Dao's attorneys will file in state court.
The legal team said they do not believe race was a factor in Dao's removal from the plane. They said the city of Chicago was also responsible for what happened to their client.
Three Chicago Department of Aviation officers were put on administrative leave this week. Chicago's aviation officers are not part of the regular police force, unlike in many other big cities. They get less training than regular officers and can't carry firearms inside the airports.
ABC News Chief Legal Analyst Dan Abrams said on Good Morning America that aviation officials could also be in the hot seat.
"There's a difference between what United did and what the police did, right? It's the police that yanked him off the plane, not United. It's the police who are now suspending those three officers, not United. It's the police who were literally taking him as he's screaming, not United. So I know we are going to continue to talk about this in the context of United Airlines, as we should, but there's another huge component to this, which is the police element," Abrams said.
He said United could avoid an embarrassing trial by offering Dao a multi-million dollar settlement out of court.
Later Thursday, Chicago aldermen, representatives from United and the union representing those aviation officers will meet to discuss Sunday's incident.
Regarding stories that have focused on Dao's background, Demetrio said his client's past is "irrelevant and will never be permissible in court."
READ MORE: Who is Dr. David Dao?
United CEO Oscar Munoz promised Wednesday, in an interview with ABC News, to review policies and promised change at the airline.
WATCH: MUNOZ INTERVIEW WITH ABC NEWS
In an initial response to the incident, Munoz seemed to blame Dao, describing him as "disruptive and belligerent." He then did an about face, offering Dao a public apology for the way he was treated. Demetrio said Thursday the apology looked "staged."
A third round of protests is expected Thursday at O'Hare. Some have called for a boycott of United.
United refunded all the tickets to passengers on board Flight 3411. They can take the compensation in cash or credits.
Munoz sent a letter to some frequent fliers in response to the incident. Here's the full text:
I've heard a lot of understandable anger and disappointment this week from customers and, as one of our most valued customers, I wanted to be sure you heard directly from me.
The awful event that occurred on Flight 3411 has elicited many responses from our customers: outrage, anger, disappointment. I share all of those sentiments. For me personally, I'd add shame. No one should ever be mistreated this way.
In addition to offering my profound apologies to the customer forcibly removed, as well as all the passengers aboard that particular flight, I also offer my sincere apology to you for not living up to the values you expect of us.
Our customers' satisfaction must be the center of everything we do and your opinion of our service is the measure of our success. We know we did not measure up, and for that we will redouble our efforts to earn your trust.
This situation has provided a humbling learning experience from which we will take immediate, concrete action. I have committed to our customers and our employees that we are going to make this right so nothing like this ever happens again.
First, we are committing that United will not ask law enforcement officers to remove passengers from our flights unless it is a matter of safety and security. Second, we've started a thorough review of policies that govern crew movement, incentivizing volunteers in these situations and how we handle oversold situations. Third, we will fully review and improve our training programs to ensure our employees are prepared and empowered to put our customers first. Our values will guide everything we do. We'll communicate the results of our review and the actions we will take by April 30.
You expect more from us and I promise we can and will be better. I am committed to putting proof behind our promise.
Thank you for granting us the opportunity to re-earn your trust.
Editor's Note: United Airlines Flight 3411 was not overbooked. Our early reporting on the incident involving Dr. Dao makes reference to the flight being oversold because that was initially believed to be the cause for the removal of passengers. It has since been learned that passengers, including Dr. Dao, were removed to make room for four crew members.
The Associated Press contributed to this report.