Americans being forced off planes against their will is actually a regular thing

Being physically dragged off a plane may be rare, but passengers are being denied boarding against their wishes every day.

United Airlines is under fire after a video surfaced of a passenger being forcibly removed from a United Express flight operated by Republic Airways.

Airlines are well within their rights to deny a passenger the right to board a plane, but they have to ask for volunteers first. If they don't get enough volunteers, the airline uses a computer system to choose passenger to block from the aircraft.

Last year alone, more than 40,000 people were involuntarily denied boarding on 12 major U.S. airlines, according to data from the U.S. Department of Transportation. Those are people who declined to take compensation, but were kicked off anyway.

Overall, the number of passengers getting bumped (either voluntarily or not) is down from a high in the late 1990s.

Still, those involuntary bumps are pretty substantial: That 40,000 is out of more than 650 million total passengers on the year. Consider it this way: one out of every 16,000 fliers. That may seem small on a percentage basis, but when you consider how many people fly in America every day, those numbers start to add up fast. More than 100 people every day around the country, just on those 12 carriers, are being denied their chance to fly, without negotiating a voluntary bump.

By law, bumped passengers can receive up to $1,350 in compensation. The average amount received was around $800, according to Airhelp.com.

Now add that 40,000 figure to more than 434,000 travelers who voluntarily gave up their seat. That's almost 1,200 per day.

United Airlines had almost 3,800 involuntary denied boardings last year, out of 86 million passengers. That percentage would rank them fifth out of 12 U.S. airlines.

The best airlines at avoiding the problem were Hawaiian, Delta and Virgin America. Each had to bump about 1 in 100,000 passengers. Delta in particular has made big improvements over the past few years in terms of reducing involuntary denials.

The three airlines with the highest number of bumped travelers were Skywest, Southwest and ExpressJet.

Overall in the industry, two trends have been emerging: (1) Compared with 15 years ago, the percentage of people being denied boarding has gone steadily down, but (2) the percentage of those people who have been denied involuntarily — that number is higher.

Delta has tried to address the issue of involuntary denials, drastically reducing the odds of a forced bump. When passengers check in online, the computer asks in advance for their bumping price. Then the airline can bump the cheapest people at their price without wasting time negotiating — or calling security.