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(CNN) —  

Dr. David Dao doesn’t recall officers dragging him off a United Airlines flight – but he does remember being emotional after seeing cell phone video of the 2017 incident that created a firestorm of controversy for the airline, he told ABC News.

“I just cried,” he told ABC in an interview shown Tuesday on “Good Morning America” when asked how he felt seeing the viral video.

Dao, speaking publicly for the first time about the encounter that left him bloodied, said that he woke up in a hospital with no memory of being taken off the plane.

Cell phone footage showed security officers dragging Dao by his arms and legs down an aisle before takeoff from Chicago’s O’Hare International Airport on April 9, 2017, after he refused to surrender his seat on the packed plane for commuting crew members.

The incident left him with a concussion, two lost teeth and a broken nose. It ultimately led to a financial settlement with United and the firing of two Chicago aviation security officers, and spurred airlines to change some ways they do business.

“The most important thing is the accident turned out the positive way,” Dao told ABC. “Airline business (is) willing to change policy.”

Gate agents first asked for volunteers to give up seats

The situation began when gate agents asked for volunteers to give up their seats on the Kentucky-bound plane for a United crew that needed to meet another flight.

Dao and his wife, who were flying home, initially agreed to take a later flight, a fellow passenger told CNN, but the couple changed their minds when they learned the next flight wouldn’t leave until the following day.

United had offered compensation to anyone willing to give up their seats; Dao apparently was chosen when not enough people volunteered. Four Chicago aviation officers arrived when he declined to leave.

In a video shot by two passengers sitting behind Dao, he repeatedly refused to get off the flight, telling officers he was a physician and had to work in the morning.

Joya and Forest Cummings told CNN that Dao was not belligerent and got only mildly upset when a second officer arrived and demanded he leave the plane, they said.

An initial letter sent to United employees appeared to blame Dao, referring to him as “disruptive and belligerent,” and praised employees for following “established protocols.” But United came under fire for how it responded as the footage went viral.

United CEO Oscar Munoz later apologized, calling the encounter “truly horrific.”

Less than a month afterward, United reached a settlement with Dao without disclosing the terms.

Dao says he forgives the officers

Dao, who has since retired, told ABC that he “had to hide” after the incident because of the attention it received.

“I (stayed) for months, months in (the) house,” he said.

He said he forgives the officers.

“I’m not angry with them. They have a job to do. They have to do (it),” he told ABC. “If they don’t do it, they may lose (their) job. So I’m not angry with them or anything like this.”

United and other airlines made changes

The dust-up had national repercussions.

United made several policy changes or clarifications. Among them: The airline won’t remove boarded passengers involuntarily – or call authorities – unless there’s a safety or security issue.

Though United said the 2017 flight was simply full, and not overbooked, Southwest Airlines announced it would no longer overbook flights in an attempt to ensure ticket-holding customers would not be booted. Delta Air Lines and United said they would, if space is needed, offer volunteers up to $10,000 to give up their seats voluntarily.

CNN’s Darran Simon contributed to this report.