Meanwhile, outraged continued to grow following the treatment of Dr. David Dao, a doctor from Kentucky, on Sunday aboard the Louisville-bound plane.
The Chicago City Council's Aviation Committee said it's working on plans to call United's CEO and Department of Aviation officials before the committee. Also, the Rev. Jesse Jackson and the Rainbow PUSH Coalition are scheduled to protest at O'Hare on Wednesday.
Tuesday evening, Asian American groups and U.S. Rep. Jan Schakowsky, D-Illinois, gathered at O'Hare to speak out in support of Dao, who is a native of Vietnam.
"It's horrible. It's not just unfriendly skies. It's unacceptable skies. That's what they're displaying," said Inhe Choi, of the Hana Center Chicago.
Schakowsky said Congressional hearings may be needed.
"Right now, we actually incentivize the airlines to overbook. This is about trying to make yet just another buck," she said.
On Monday, United called Dao "disruptive and belligerent." On Tuesday, company CEO Oscar Munoz issued an apology calling the incident "truly horrific" and that he offers his "deepest apologies." He ordered a review of its overbooking policies and partnerships with airport law enforcement.
Munoz will appear on "Good Morning America" for an exclusive interview Wednesday morning on ABC7.
WATCH: DR. DAO'S FAMILY RELEASE STATEMENT
Dao was being treated Tuesday at a Chicago hospital for his injuries and the family asked for privacy.
His family released a statement through a Chicago attorney Stephen L. Golan: "The family of Dr. Dao wants the world to know that they are very appreciative of the outpouring of prayers, concern and support they have received. Currently, they are focused only on Dr. Dao's medical care and treatment."
The family is also being represented by Chicago aviation attorney Thomas A. Demetrio.
RAW VIDEO: UNITED PASSENGER DRAGGED OFF FLIGHT AT O'HARE
On Tuesday, White House Press Secretary Sean Spicer called it an "unfortunate incident" and that United's handling of the situation was "clearly troubling."
Mayor Rahm Emanuel said in a statement Tuesday that, "Anyone who saw that video had the same reaction: this was completely unacceptable at every level. I appreciate that Ginger took swift action at the Department of Aviation, and her team is already hard at work on a thorough investigation - in partnership with the airline - to ensure nothing like this ever happens again."
Alderman Michael Zalewski (23rd Ward) called for a meeting of the Chicago City Council Committee on Aviation at 1 p.m. Thursday where aldermen are expected to discuss a resolution to direct representatives from United Airlines and the Chicago Department of Aviation to appear before the committee to address the incident.
Zalewski said that the aviation security officers are typically not supposed to be on planes and any law enforcement action on a plane should be done by a Chicago police officer.
Congressman Dan Lipinski (D-Chicago) said: "I think it is unacceptable what United did to that passenger having him pulled off that flight. It may take federal action on this issue so it doesn't happen again."
UNITED FLIGHT 3411
Cellphone video shows the incident aboard the plane waiting to depart from O'Hare. Officers could be seen grabbing a screaming Dao from a window seat, pulling him across the armrest and dragging him down the aisle by his arms. The airline was trying to make room for four of its employees on the Sunday evening flight to Louisville.
Other passengers on Flight 3411 are heard saying, "Please, my God," ''What are you doing?" ''This is wrong," ''Look at what you did to him," and "busted his lip."
An initial statement in response to the incident said the flight was "overbooked." The airline clarified Monday, calling the problem a "crew-positioning issue."
United needed to get a four-person crew for Republic Airlines, which was operating the United Express flight, to Louisville Sunday. Otherwise, United would have had to cancel flights out of Louisville on Monday.
Passenger Audra D. Bridges posted the video on Facebook. Her husband, Tyler Bridges, said United offered $400 and then $800 vouchers and a hotel stay for volunteers to give up their seats. When no one volunteered, a United manager came on the plane and announced that passengers would be chosen at random.
"We almost felt like we were being taken hostage," Tyler Bridges said. "We were stuck there. You can't do anything as a traveler. You're relying on the airline."
OFFICER PLACED ON LEAVE
On Monday, the Chicago Department of Aviation said that an officer has been placed on leave pending a "thorough review of the situation."
The department released an updated statement Tuesday, "The Department of Transportation's Office of Aviation Enforcement and Proceedings began its initial review of United Airlines Express Flight 3411 on April 10. The Department remains committed to ensuring that airlines comply with consumer protection regulations and will not speculate during the review process on this matter."
There are about 300 aviation security officers working at O'Hare and Midway. They receive about four months of training at the Chicago Police Academy.
The incident has caused some United customers to cut or shred their membership cards.
"It honestly make me feel like I don't want to fly United and I'm absolutely going to try not to going forward because it really makes me question how they handle things," said Kelsey Bourgeois of Care2.
Bourgeois started an online petition has over 20,000 people who are asking the CEO of United resign.
"It seems like employees should get the leftover seats. Why couldn't they get them a car? Why couldn't they put them on a flight on a different airline? There's just a million different things they could have done besides this," said Bourgeois.
FULL STATEMENT BY UNITED AIRLINES CEO OSCAR MUNOZ:
"The truly horrific event that occurred on this flight has elicited many responses from all of us: outrage, anger, disappointment. I share all of those sentiments, and one above all: my deepest apologies for what happened. Like you, I continue to be disturbed by what happened on this flight and I deeply apologize to the customer forcibly removed and to all the customers aboard. No one should ever be mistreated this way.
"I want you to know that we take full responsibility and we will work to make it right.
"It's never too late to do the right thing. I have committed to our customers and our employees that we are going to fix what's broken so this never happens again. This will include a thorough review of crew movement, our policies for incentivizing volunteers in these situations, how we handle oversold situations and an examination of how we partner with airport authorities and local law enforcement. We'll communicate the results of our review by April 30th.
"I promise you we will do better.
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.