Overbooking on flights happens all the time. Empty seats cost airlines money, so they offset the number of passengers who miss flights by selling too many tickets.In this case, the problem arose because United decided at the last minute to fly four members of staff to a connection point and needed to bump four passengers to make way for them.
When there is an overbooking issue, the first step is to offer an inducement to the passengers to take a later flight. On Sunday passengers were offered $400 , a hotel room for the night, and a flight the following afternoon.
When no one took the offer, the amount was upped to $800. Still no one bit, so a manager boarded the flight and informed passengers that four people would be selected to leave the flight.
That selection is based on several factors, but frequent fliers and higher fare-paying passengers are given priority to stay aboard, a spokeswoman for United confirmed.
A couple who were selected agreed to leave the plane voluntarily. A third passenger, reportedly the wife of the man who was forcibly removed, also agreed. The man, who said he was a doctor and had to see patients in the morning, refused.
At this point, the airline could have identified another passenger for removal or raised its offer anywhere up to a maximum of $1,350.
Erin Benson, a spokeswoman for United, could not confirm whether other passengers were sought. She did confirm that no offer was made above $800, but could not comment on why.
According to eyewitnesses, the man who refused to be ejected said he was a doctor and he had appointments to keep the following day, though this has not been confirmed. This was a Sunday night flight; the next flight on offer didn't leave until 15:00 on Monday.
An eyewitness said the man was "very upset" about the possibility of being bumped and attempted to call his lawyer. An airline manager told him that security would be called if he did not comply.
At this point, security officers came to speak to him, first one then two more. As the video shows, their conversation ended with the man being yanked from his seat onto the floor and dragged off, blood visible on this face.
United is technically within its rights to forcibly remove the man for refusing to leave the flight, and the step is part of the airline's carriage guidelines, but such instances are extremely rare. US fliers have become resigned to chronic delays and poor service, according to Mr Leocha, and a lack of readily available information about their rights meant they were too dependent on the airline managers in situations like these.
"Our expectations have been driven so low that passengers have begun to accept it," he said. "What they shouldn't have to accept is being dragged off the flight to make way for an employee."
One of the security officers involved in the incident was suspended on Monday afternoon, pending a review, said the Chicago Department of Aviation in a statement.
The actions of the officer were "obviously not condoned by the Department", the statement said.
Whatever happened on the flight - and the details will undoubtedly emerge in the coming days - it was a bad day for United, Mr Leocha said. The airline had only recently been at the center of another controversy, when a fortnight ago it refused to let two girls board because they were wearing leggings.