For a few moments last month, a crowded gate at the San Juan, Puerto Rico, airport turned into an auction in reverse.
A flight to New York City was overbooked, and an airline representative was offering $100 vouchers to passengers who would agree to take the next available flight. Nobody took the deal. The amount offered went up and up, all the way to an impressive $600, before four travelers agreed to stay.
"Dollar signs lit up in people's eyes," recalls David Lytle, editorial director of the travel website frommers.com, whose flight was leaving from a nearby gate.
There must have been worry, too. If no one gave up his or her seat, four passengers would have faced one of the most dreaded hassles in all of air travel - being involuntarily bumped and, at least for a time, stranded.
Thanks to airlines eager to fill every seat, the number of bumpees is rising. Eighteen US carriers involuntarily bumped 1.33 out of every 10,000 passengers during the first six months of this year, up from 1.21 in 2006, according to federal statistics.
The rate was just .72 passengers per 10,000 in 2002, during the travel slump that followed 9/11.
In the grander scheme of air travel in the United States, these numbers are minuscule. Airlines are much more likely to lose your luggage than bump you from a flight. (For every 10,000 airline passengers in the first six months of this year, 73 bags were reported lost, stolen, or damaged.) Even so, the delays are yet another aggravation for passengers already coping with jampacked planes.
It may seem illogical that airlines sell more seats than they have. Movie theaters, by contrast, don't overbook: If you buy a seat, it's yours.
The difference is that tickets for airlines are infinitely changeable while a movie ticket for, say, 4:15 p.m. can't be changed, says Peter Belobaba, who studies the airline industry at MIT in Cambridge, Mass. Some plane tickets can be refunded even if you don't take the flight, and others can be changed at the last minute without a penalty, especially if the ticket cost a lot of money.
"The airlines use complex statistical models to predict how many people are going to show up for a given flight," says Steve Call, director of a travel and tourism degree program Ohio University-Ironton. "Over the years, they've determined they need to oversell a flight by X amount of seats because there will be no-shows."
Cash for those bumped involuntarily
But sometimes there are more people than seats, and airline representatives start offering vouchers for future travel. If no one accepts, airlines will kick one or more passengers off the flight, rebook them if possible, and pay them up to $200 or $400 in cash if their landing time is delayed more than an hour.
Credit a certain consumer advocate for the payment scheme. "Some airline made the mistake of involuntarily denying [a seat to] Ralph Nader in the early 1970s," says Mr. Belobaba. "He sued. That's how this whole policy came about."
There may be some good news in the wings: The US Department of Transportation is considering whether to raise the amount of cash that passengers receive if they're bumped involuntarily. Under one proposal, involuntary bumpees would be due up to $1,248.
Cash, of course, won't buy every passenger's happiness, especially if they're in danger of missing a wedding or a World Series. If you don't want to be bumped, there are some nearly surefire ways to avoid it.
"Make sure you have a seat assignment," advises Belobaba, "and get to the airport on time. It's always the laggards and those who don't pay attention to what they're doing who get involuntarily bumped."
Many airlines will allow you to go online and check how full a flight is; that could help you avoid a chronically overbooked flight. And Belobaba suggests that passengers remember the old adage: "You get what you pay for."
"People don't realize there is a pecking order as to whom airlines deny boarding to, based on what they paid [and] whether they're an elite member or bought tickets through some third-party wholesaler" such as Priceline, Belobaba says.
If you have a flexible schedule, you can volunteer to be bumped. Some passengers mention to the airline representative that they're willing to be bumped when they check in and sit close to the counter so they can be first in line if the airline needs volunteers.
Volunteers should read the fine print
Be careful, however, to keep a close eye on the deal you're being offered. Vouchers have restrictions and blackout dates, says AirTran Airways spokeswoman Judy Graham-Weaver.
To use the voucher, you may end up having to book by phone and pay a special fee. And there will be an expiration date.
Another piece of advice: Be careful if you ask to be bumped off a popular flight. "The airlines are flying full airplanes," Mr. Call says. "You try to go on a space-available basis, and it might take you a day or two to get where you want to go."
Even if you have time to spare and walk out of the airport with airline vouchers for lodging and food, bumping can lead to no end of annoyances. Hotels may be full, and the vouchers might limit you to unpalatable airport food.
But if you're the kind of traveler who enjoys the unexpected, getting bumped could lead to adventure, as Rough Guides senior editor AnneLise Sorensen found several years ago in New Delhi.
After a four-month solo backpacking trip, she planned to fly to Paris and find a world of "steaming cafe cremes and timely trains."
In the end, it was luxury
Instead, the flight was overbooked and she agreed to give up her seat for a family on their way to see an ailing relative.
"Call it karma, but I had unwittingly walked into a budget traveler's dream: myself and the other bumpees were transported to a luxury hotel - sparkling pool, high-thread-count sheets - and handed meal vouchers for the generous buffet," she recalls. "To sweeten the deal, we were paid a daily stipend of over $100. This went on for several days. Our only duty was to board the shuttle to the airport every morning, with our luggage, to get in line to give up our seat."
Those who were bumped happily accepted the deal "again and again," Ms. Sorensen says, adding three words that must rarely pass the lips of any traveler: "Paris could wait."