So, it turns out United won't be fined for that passenger-dragging incident

Federal officials have decided not to punish United Airlines after all, over a now infamous incident in which a passenger was dragged off an overbooked flight.

An investigation by the Department of Transportation found no evidence that United violated the passenger's civil rights, according to a report by the Associated Press.

A video of David Dao went viral earlier in April after he was seen forcibly dragged off a plane, an incident which left him with a broken nose and a concussion.

This Tweet is currently unavailable. It might be loading or has been removed.

The Transportation Department told United of its decision in a May 12 letter that was obtained through non-profit organization Flyers Rights, through a Freedom of Information Act request.

The department also added that it found no proof that United discriminated against Dao, an Asian-American, on the basis of race.

Paul Hudson, president of Flyers Rights, criticized the decision.

"For the Department of Transportation to conclude that United's conduct did not warrant an enforcement action is a dereliction of duty," he said.

United apologized again on Wednesday, saying the incident "should never have happened."

Dao was on his way to Louisville from Chicago on April 9 when United decided it needed to make room for its flight attendants. United first asked for volunteers, then randomly selected passengers to be removed off the flight.

Dao was one of the passengers who was asked to leave, but he refused, saying he had to get to work the next day. As a result, he was dragged down the airplane aisle by airport security.

United later settled with Dao for an undisclosed sum of money.