Following a highly publicized incident in which a passenger was physically dragged off of a flight to provide a seat for an airline employee, air carriers reduced the practice of "bumping" passengers from overbooked flights.
But an NBC Responds analysis of federal aviation data finds Involuntary Denied Boarding, or "bumping," never actually stopped. And it's shot up significantly this year.
You may remember the April 2017 removal of Dr. David Dao from a United Airlines Express flight originating in Chicago. The situation was caught on video by passengers.
Dr. Dao had a paid seat, but airport officers removed him from the flight after the airline decided to give his seat to a crew member.
After the Dr. Dao incident stirred the flying public, many domestic carriers publicly changed their policies. Among them was Southwest Airlines.
By 2018, the number of passengers involuntarily taken off a flight fell more than 65%. But an NBC Responds review of federal data found that "bumping" is now bouncing back.
The U.S. Department of Transportation data shown here cover the first six months of 2019. In that time, airlines bumped 13,104 paying passengers -- more than all of 2018.
We asked airlines: why the jump in bumps?
American Airlines, which bumped the most passengers -- 8,760 per federal data -- pointed to two problems: a labor dispute that disrupted its schedule, and a shortage of planes due to the Boeing 737 MAX being grounded.
Southwest Airlines, which bumped 2,525 over the first six months of the year, blamed various "operational challenges," including the Boeing 737 MAX.
Those reasons seem to conflict with information on both airlines' websites, where they say passengers previously scheduled for flights on 737 MAX aircraft will be "proactively notified" or "automatically accommodated."
Federal data show that passengers are still being blindsided at the gate, and denied their seats.
Andrew Applebaum, an attorney with the air traveler advocacy group FlyersRights.org, says he suspects airlines still haven't fully reduced ticket sales to match their smaller fleets.
"We don't buy the airlines' argument that the increased number of Involuntary Denied Boardings is due to the Boeing MAX situation," Applebaum told NBC Responds.
"The airlines' motivation is pure profit," Applebaum said. "They're able to sell more tickets. If a passenger has to be bumped, the passenger is entitled to a small amount of compensation. That's worth it to the airlines."
Southwest Airlines told us its team "strives for zero [bumping] each day."
American Airlines said it has been bumping fewer passengers since the summer ended. It pointed us to a statement in which CEO Doug Parker discussed the airline's performance so far in 2019 -- including the schedule disruptions. "We are taking decisive action to correct this," Parker said. He also said he is "...excited about our prospects for 2020."
The Airlines say they generally need to overbook flights to account for 'no-shows' -- passengers who cancel or miss their flight. But when everyone shows up to come aboard, someone's got to go. So, how do airlines decide who gets bumped?
Their exact formulas are proprietary, so we searched their ticket contracts for clues.
Some airlines consider how much you paid for your seat when choosing who to bump. If you buy the cheapest fare -- sometimes sold as "basic economy" -- you might be the first to go, so the airline can give your seat to someone else who paid a higher fare.
Something else that stands out: your check-in time is crucial. The last passengers to check in can be the first ones bumped. So, if you want to keep your seat, check in as early as possible.
If all else fails and you're pulled from a flight, federal law says you're entitled to compensation. How much you get hinges on the ticket price, and how long it takes the airline to get you to your destination. The maximum payment, by law, is $1,350 cash. But you can ask for more -- perhaps in airline vouchers or gift cards if you volunteer to give up your seat. You might be able to negotiate as a volunteer. Click here to see how federal law dictates the amounts airlines must pay you if you ultimately get bumped.
One final note: if you get bumped and the airline re-books you on a flight that gets you to your destination within an hour of the original scheduled time, you may not get anything. Keep that in mind when the call for volunteers comes up at the gate.