But first, a few details to flesh out the story. According to one flyer, soon after the passengers boarded the flight, United announced that four of them would have to give up their seats to make room for United employees commuting to work a flight out of Louisville. After the offer was raised to $800, and nobody was willing to leave the flight (perhaps because it would require missing a full day's work without a compelling excuse), somebody from United announced that a computer would randomly select four people to leave the plane. When the man in the video, a doctor, was selected, he refused to leave his seat, saying he had to see patients the following morning. United called officers to the scene. The rest is now a matter of digital record.

Can United really do this? Legally, the airlines can turn away paying customers, and they do it thousands of times a year. Airlines often overbook flights to account for the likelihood that passengers won’t show up, and, although this can be extremely annoying, it is also legal and might even contribute to lower prices for tickets, because it increases the likelihood that planes will be filled to capacity. According to its contract of carriage, United can deny boarding on oversold flights if passengers don’t accept compensation. Here is the key part of the contract language, under Rule 25 Denied Boarding Compensation (which, notably, says nothing about forcibly removing passengers after they have boarded the plane to make room for United workers):

Boarding Priorities - If a flight is Oversold, no one may be denied boarding against his/her will until UA or other carrier personnel first ask for volunteers who will give up their reservations willingly in exchange for compensation as determined by UA. If there are not enough volunteers, other Passengers may be denied boarding involuntarily in accordance with UA’s boarding priority.

That “boarding priority” protects minors and disabled people and makes special commendation for “fare class [and] status of frequent flyer program.” In other words: Don’t worry, First Class folks, you’re safe.

It’s important to note that this is a very rare occurrence. Several sources track the number of people who are denied boarding each year in the United States due to overbooking, and they all say it is declining steadily. The share of passengers denied boarding rose until the late 1990s to about 1 in 500, but it's fallen to about one in a thousand, according to the Bureau of Transportation Statistics. According to another report, the 2017 Airline Quality Rating (released, incredibly, just this morning), involuntary denied boardings are affecting about six passengers per 100,000.

But although this incident was unusual in many respects, it was also representative of an airline industry that has considerable power over consumers—even if the use of force is more subtle than a group of security professionals wrestling a passenger to the floor.