April 11, 2017 - 7:34pm
The CEO of United Airlines has said that employees "followed established procedures" in an incident which saw a passenger dragged off an overbooked US domestic flight.
In a letter to employees, Oscar Munoz said he was "upset to see and hear about what happened".
But he said that the passenger had been "disruptive and belligerent".
The airline earlier said that it was investigating what happened after videos provoked a social media outcry.
The footage taken inside the airliner shows a man being pulled out of his seat and dragged down the aisle. He is later seen with blood on his face.
The man has not been officially identified but a passenger who sat next to him told BBC Radio 5 Live that he said he was originally from Vietnam and had been living in Louisville, Kentucky, for about 20 years. He said he and his wife were both doctors.
The flight from Chicago to Louisville on Sunday evening had been overbooked.
The airline wanted to get four passengers to leave the flight to make room for four staff members.
Mr Munoz has faced criticism on social media for his response to the incident.
He told staff in the private email that he was "upset to see and hear about what happened" but defended United employees.
"Our employees followed established procedures for dealing with situations like this," the Associated Press quoted the email as saying.
"While I deeply regret this situation arose, I also emphatically stand behind all of you, and I want to commend you for continuing to go above and beyond to ensure we fly right."
Mr Munoz wrote that the passenger refused to voluntarily leave the plane, with staff "left with no choice but to call Chicago Aviation Security Officers to assist in removing the customer from the flight".
Only last month, trade magazine PRWeek named Mr Munoz as 2017 US Communicator of the Year, but his airline's handling of the fallout from this incident is being mocked on Twitter.
Users are posting under the hashtag #NewUnitedAirlinesMottos.
Some initial reports said the manhandled passenger was Chinese-American, and outrage quickly erupted on Chinese social media.
Jayse D Anspach, who posted footage that went viral, tweeted: "#United overbooked and wanted four of us to volunteer to give up our seats for personnel that needed to be at work the next day."
"No one volunteered, so United decided to choose for us. They chose an Asian doctor and his wife."
"The doctor needed to work at the hospital the next day, so he refused to volunteer," Mr Anspach added.
"Ten minutes later, the doctor runs back into the plane with a bloody face, clings to a post in the back, chanting, 'I need to go home'."
A video that appears to show the man back on the plane, dazed and with blood around his mouth, saying "just kill me", has also emerged online.
One of the three security officers involved has been "placed on leave", the Chicago Department of Aviation said, and his actions were "obviously not condoned by the Department".
The department also said it would carry out a review into the incident, which it said was "not in accordance with our standard operating procedure".
The US Department of Transportation is reviewing whether United complied with rules on overbooking,
"While it is legal for airlines to involuntarily bump passengers from an oversold flight when there are not enough volunteers, it is the airline's responsibility to determine its own fair boarding priorities," a spokesperson said in a statement reported by Reuters.
United said it was trying to talk to the passenger directly in order to "further address and resolve this situation".