http://www.cnn.com/2017/04/11/travel/questions-united-trnd/
3. Can an airline legally kick a paying customer off a flight?
Actually, yes. According to data from the US Department of Transportation, 46,000 passengers were involuntarily bumped from flights in 2015, the most recent year for which data is available. This happens because most carriers purposefully overbook their flights knowing people sometimes won't show up.
When an airline chooses to clear out seats on a flight, they are required to go through a process:
First, according to the Department of Transportation, they have to see if anyone will give up their seat voluntarily. They typically offer compensation, such as a voucher for another flight.
Also, as mentioned above, while airlines can legally kick people off,
each airline has its own general guidelines as to who they kick off and why.
4. Why didn't they just offer the man more money?
This is one of the biggest questions people have about the incident. According to passenger accounts, United's offer for compensation stopped at $800 -- a rather small sum for such an expensive inconvenience, and certainly not a sum worth the amount of ire United has faced in the last few days.
According to DOT regulations, there is no "mandated form or amount of compensation that airlines offer to volunteers."
"Carriers can negotiate with their passengers for mutually acceptable compensation," the regulations read.
Now, where it gets really interesting is when passengers are bumped involuntarily, like the four people on Sunday night's flight. Depending on the length of the delay, the airline may have to pay $1,350 for the inconvenience.
"If the substitute transportation is scheduled to get you to your destination more than two hours later (four hours internationally)... the compensation [is] 400% of your one-way fare, $1350 maximum."
That maximum would fit United's predicament, since the next scheduled flight to Louisville was a full day later.
5. What can you do if it happens to you?
First and foremost, you can sue. DOT regulations clearly state that you can take the airline to court for more money if you feel the maximum compensation didn't fit the value of the situation. They do advise, however, that if you intend to sue you absolutely should not accept any flight vouchers or cash any compensation checks the airline offers you.
"Once you cash the check (or accept the free flight), you will probably lose the ability to pursue more money from the airline later on," the DOT's Consumer Guide to Air Travel states.
The DOT even has a guide to navigating small claims courts -- a recommended option for passengers who experience severe inconvenience because of an involuntary flight bump.