Frequent fliers could be left with a pocketful of worthless mileage certificates if they don't act by Dec. 31.
Last year, more than 20 billion miles expired on Dec. 31, according to Tammi Scheetz, research director for Inside Flyer, a Colorado-based magazine.
And the total could be even greater this year, she said.
Airline travelers should check all their certificates and mileage statements -- as well as free hotel stays and airline upgrades -- to make sure that they still will be good in 1996.
"You snooze, you lose," said Ms. Scheetz. "Don't let your miles expire."
A few airlines impose expiration dates on mileage when it's earned, typically three years. If you earned the mileage in 1992, it will expire by the end of 1995.
Typically, airlines allow passengers to bank their points and trade them for certificates, which, in turn, can be turned into free tickets. Airlines often impose expiration dates on certificates once they're issued.
And last year, as many airlines raised the minimum level needed for a free ticket, travelers cashed in miles for certificates, which required them to book a flight by the end of this year. In most cases, they will have a year to complete the travel on those flights, however.
If your points are expiring but you don't have quite enough for a few tickets, you may be able to combine them with newer mileage to get a certificate or free ticket.
In addition, mileage points make a great gift, Ms. Scheetz said. They can be passed to a friend or donated to charities that several major airlines have set up for that purpose.
Introduced by American Airlines in 1981, frequent-flier programs were designed to create passenger loyalty by giving repeat customers free trips or upgrades to first class.
Industrywide, membership in the programs has soared from 1.8 million to nearly 35 million today.
In recent years, airlines have stepped up their frequent-flier promotions, offering more ways to accumulate points -- and increasingly creative ways to use them.
In addition, corporate tie-ins have provided fliers many more ways to earn points: by using an affinity credit card, placing a long-distance call, renting a car or staying at a hotel.
Today, only 35 percent of all frequent-flier points are earned through flights.