Doctor dragged off United Airlines flight after watching viral video of himself: 'I just cried' Dr. David Dao spoke in his first public interview since the incident.

The Kentucky doctor seen in a viral video being forcibly removed off an United Airlines flight has spoken publicly for the first time since the 2017 incident, telling ABC News that while the ordeal caused distress for him and his family, he doesn't regret standing his ground because it caused the airline to take a closer look at its policies.

On April 9, 2017, David Dao was traveling from Chicago O'Hare International Airport to Louisville, Kentucky, on United Airlines Flight 3411 and already was in his seat with his seat belt fastened when an airline employee informed him that he would need to deplane because the flight was overbooked, he told ABC News.

Fellow passengers took cellphone videos of a bloodied Dao being dragged off the plane.

Even months after the incident, Dao found the video hard to watch.

"I just cried," he said.

Dao said he stood his ground and refused to get off the plane because he felt he was being discriminated against and was trying to get back to Kentucky to oversee the opening of a clinic he founded for U.S. veterans. He and his wife started the clinic as a way to thank American servicemen and women, because he was plucked out of ocean waters by the U.S. Navy as he fled communism in his home country of Vietnam about 44 years ago, he said.

He said while in his seat, belt still fastened, he was on the phone with a friend, asking for advice on whether he should get up, when the next thing he knew, he was being pulled from his seat. He doesn't remember anything after he bumped his head on the low ceiling.

"After that, to be honest, I don’t know what happened," he said, adding that he heard a "big noise" and later woke up in the hospital with a trauma team surrounding him.

The first few months were "horrible," he said. He suffered a concussion, lacerations to his mouth and nose, and several of his teeth were knocked out, he said. He was put on suicide watch by hospital staff and later spent months learning to walk again, he said.

Dao relied on his faith during his recovery, he said, adding that he made a promise to God that if he got better, he would devote his time to charity work. Since then, he has helped residents in Texas displaced by Hurricane Harvey and traveled to Vietnam and Cambodia to help install solar power in villages with no electricity, he said. Even in the Far East, people knew his story, he said.

One elderly man approached him and asked, "You the one on airplane?" Dao said.

"That touched me," the doctor said, holding back tears.

Dao still struggles with issues sleeping and with his concentration and balance, he said. While he'd run more than 20 marathons before the incident, now he can only do about 3 miles -- with at least one of them by walking, he added.

While United's initial statement labeled Dao as "belligerent," the airline later apologized, vowing to conduct a "thorough review" of the "truly horrific event."

Oscar Munoz, the CEO of United Airlines, said he felt "shame" when he saw the video.

"This will never happen again," Munoz told ABC News' "Good Morning America" in an interview three days after the incident. "We are not going to put a law enforcement official onto a plane to take them off … to remove a booked, paid, seated passenger. We can't do that."

When asked whether United should have done anything differently, Dao said the airline employees could have explained their reasoning for booting him from the flight "nicely" and "reasonably."

"That makes a difference," he said.

Still, the retired doctor said his ordeal actually was "positive" because the airline was willing to take a hard look at its policies and change them.

"Everything happens with a reason," he said.

Weeks after the incident, the airline offered Dao a settlement that his attorney at the time, Thomas A. Demetrio, described as "amicable," which Dao accepted. The settlement included a provision that the amount offered remain confidential.

Dao said he decided to speak publicly for the first time to thank his supporters all over the world.

United Airlines issued a statement to ABC News, saying the changes they've implemented since the incident "better serve out customers and further empower our employees."

"Flight 3411 was a defining moment for United Airlines and it is our responsibility to make sure we as a company and all of our 90,000 employees continue to learn from that experience. The changes we have implemented since that incident better serve our customers and further empower our employees," according to the statement from United Airlines. "This year, we are focused more than ever on our commitment to our customers, looking at every aspect of our business to ensure that we keep their best interests at the center of everything that we do. As our CEO Oscar Munoz has said, we at United never want anyone in the United family to forget the experience of Flight 3411. It makes us a better airline, a more caring company and a stronger team."