Record numbers of travelers are taking to the skies. So what happens if there's no seat for you?

Airlines have for years sold more seats than they have on board, a legal practice that has allowed them to manage inventory: No airline wants a seat to go empty if a traveler cancels at the last minute.

Luckily, the rate of airline bumping has declined in recent years to a record low. Last year, U.S. airlines denied boarding to 0.3 people per 10,000 passengers, according to the U.S. Department of Transportation.

Airlines have tried to offer passengers more money, to avoid having to choose passengers to take later flights themselves.

In April 2017, passenger David Dao was violently dragged off a United Express flight after he refused to make room for commuting crew. The fiasco sparked an uproar from consumers. In the wake of the scandal, United said it would raise the amount of compensation it offers to travelers who volunteer to take later flights to as much as $10,000. One passenger received a travel voucher for that amount in March when there weren't enough seats on her flight. Delta announced a similar ceiling in compensation for bumped travelers.