A video posted to Facebook on Sunday night is causing outrage at United Airlines as it shows security forcibly removing a screaming, bloodied man from a plane – all because the flight was overbooked.

Flight 3411 from Chicago's O'Hare Airport to Louisville, Kentucky was full, passengers said, and customers were asked to voluntarily give up seats in exchange for money, a stay in a hotel and a flight the next day. One passenger told the Louisville Courier-Journal that passengers boarded anyway but were told that four United employees needed to be on that flight instead.

When none of them volunteered to vacate, United upped the amount being offered. However, when no-one came forward still, passengers were informed that a computer would randomly select passengers to disembark, according to an observer.

One of those chosen said he was a doctor and needed to see patients in Louisville in the morning, according to eyewitnesses, but United allegedly did not let up and called in security to escort the man off the place. When he still would not leave, the video shows what happened next.

A security man grabs the man forcibly so that his head hits the armrest across the aisle, before he is dragged off the place.

The video ends abruptly but the passenger told the news site the man was let back on the plane, though he seemed disorientated and bloodied. A witness said he ran to the back of the plane and passengers were asked to disembark while a medical crew dealt with the man.

Another video of the incident posted to Twitter shows the man's face looking bruised and bloodied as he is dragged along the aisle.

A spokesperson for United told IBTimes UK over email: "Flight 3411 from Chicago to Louisville was overbooked. After our team looked for volunteers, one customer refused to leave the aircraft voluntarily and law enforcement was asked to come to the gate.

"We apologize for the overbook situation. Further details on the removed customer should be directed to authorities."