The fastest way to get a free airline ticket may be the most unexpected: Give up your seat at the last minute.

What is Bumping?
To be bumped is to be denied a seat on a plane when you have a confirmed reservation. It results from overbooking, an airline practice designed to fill the empty seats that absent passengers leave behind. Bumping first became a major issue in April 1972, when the consumer advocate Ralph Nader was put off an Allegheny Airlines (now US Airways) flight from Washington to Hartford and missed a fundraising rally. He sued Allegheny, charging that it had fraudulently represented his reservation as confirmed. He won $10 in actual damages and $25,000 in punitive damages for the rally's sponsors.

The Department of Transportation requires commercial airlines flying 60 passengers or more and originating in the United States to seek out volunteers before bumping anyone involuntarily. Such volunteers can receive lucrative rewards, from cash to free air vouchers. In general, the longer the delay, the better the payoff. Some airlines will even offer meals, free drink coupons, free headsets on the next flight, an upgrade to first-class, a free long-distance phone call, or admission into the swanky airline clubs.

The Transportation Department closely monitors bumping. Its statistics show that about 4% to 5% of all airline passengers are bumped voluntarily; and less than 1% are bumped involuntarily. The average in 2001 was about 20 passengers involuntarily bumped per 10,000 passengers.

How to Get Bumped
First, determine what flights are most likely to be overbooked. They include:

- Routes frequented by business travelers, departures after noon on Fridays or on Sunday evenings.
- Pre- and post-holiday flights.
- Transcontinental nonstops.
- Popular routes.
- Routes that have scant nonstop or direct service with no change of planes.

If you're really serious, you can choose an airline that bumps the highest percentage of passengers. See the latest oversales figures in the Consumer Report from the DOT.

Get to the gate early. Airline rules typically state that if you don't arrive at least 10-20 minutes before the scheduled departure, you will forfeit your reservation and have to fend for yourself. In most cases, incidentally, airlines are not required to compensate you for the missed flight.

Don't hassle the gate attendants. Arrive early and let them know you're a willing volunteer, then simply remain near the gate where they can contact you if needed. Asking about the status of the flight every five minutes or becoming rude or impolite will not make the attendants very anxious to hand you cash or free flight vouchers.

How to Avoid Bumping
If you have obligations in your destination city and absolutely cannot afford to be bumped from a flight, arrive as early as possible to the airport, especially if you're taking a popular route. The last to check in to the flight are typically the ones who find themselves bumped involuntarily. If you're at the gate before the majority of the passengers have checked in, your chances of retaining your original reservation are favorable.

What the Law Says
The Transportation Department has specific rules governing overbooking procedures. From the DOT's Consumer Guide to Air Travel:

The airline must give you a written statement describing your rights and explaining who gets on an oversold flight and who doesn't. If the airline arranges substitute transportation that gets you to your final destination within an hour of your original scheduled arrival time, there is no compensation.

If the substitute plane is scheduled to get you there from one to two hours late on domestic flights and one to four hours internationally, the airline must pay you at least the equivalent of your one-way fare to your final destination, with a $200 maximum. If more than two hours domestically or more than four internationally, or if the airline doesn't make substitute arrangements for you, the compensation doubles, with a $400 ceiling. You can demand payment on the spot, and if you feel entitled to more than the rules require, you can try negotiating with the complaint department.

Before you count your rewards, however, be aware that you must have a confirmed reservation. An "OK" in the status box of your ticket will suffice, even if the airline can't find your reservation in the computer.

Also, federal bumping rules do not apply to charters, planes with 60 seats or fewer or smaller aircraft that are substituted for originally scheduled ones. They don't apply to inbound flights to the United States or to flights between foreign cities, but airlines or foreign countries may have rules of their own