Two US security officers have been fired after a man was forcibly removed from a United Airlines flight back in April.

Dr David Dao was taken off the overbooked plane after he was asked to give up his seat.

He hit his face on an armrest, resulting in him sustaining a concussion, a broken nose, and the loss of two teeth.

Footage of Dr Dao being dragged from the cabin went viral.

@united @FoxNews @CNN not a good way to treat a Doctor trying to get to work because they overbooked pic.twitter.com/sj9oHk94Ik

— Tyler Bridges (@Tyler_Bridges) April 9, 2017

The Chicago Office of the Inspector General (OIG) found three Chicago Department of Aviation (CDA) security officers and one aviation security sergeant violated rules during the incident.

Dr David Dao was taken off the United Airlines service back on April 9th, after he was asked to give up his seat.

The OIG investigation found the first security officer "escalated a non-threatening situation into a physically violent one" by forcefully removing the passenger.

The investigation also established that the second officer made "misleading statements" in two reports, and a third officer made "material omissions" in a report regarding the first officer's forceful removal of the passenger.

The Chicago Department of Aviation has discharged the first security officer and the sergeant - while five-day suspensions were given to the second and third security officers.