"United pilots are infuriated by this event," the pilots union says. "This should not have escalated into a violent encounter."
The union slams what it calls a "grossly inappropriate response by the Chicago Department of Aviation."
Dao was knocked unconscious and dragged off a United plane after refusing to give up his seat on Sunday for an employee of the airline.
Dao, a 69-year-old Kentucky physician suffered a “significant” concussion, a broken nose, damaged sinuses, and had two teeth knocked out as he was forcefully removed from the flight.
Dr. Dao refused to leave the Louisville-bound flight that was departing from Chicago, saying he was a doctor and had patients to see Monday morning.
After he was dragged off the plane, he somehow wound up back on the aircraft, shouting, “I want to go home" as blood poured from his mouth and streaked across his face.
Every passenger was ordered off so they could clean up the plane. The aircraft eventually departed.
The CEO of United Airlines, Oscar Munoz, has since apologized for the incident.