Loosening Rules for Frequent-Flier Miles

“Use it or lose it” is getting to be an obsolete adage when it comes to frequent-flier miles, as big airlines liberalize expiration policies.

Just last week United Airlines, the world’s biggest, said miles accumulated under its Mileage Plus program will no longer automatically expire after three years--providing that members redeem miles, take a flight on United (or its 20-some airline partners), or use the services of any of its thousands of car-rental, hotel or other partners, including MCI, during that period. Mileage Plus claims about 37 million members. (The change affects fliers logging fewer than 20,000 miles; higher mileage members have been able to “roll over” miles.)

The week before, American Airlines, the world’s second largest, announced a similar policy change for its program, which claims more than 35 million members. And earlier this year, Northwest switched off its program’s expiration dates to match the policies of partner Continental. Southwest Airlines remains one of the few U.S. holdouts. Its earned miles expire after one year, and a spokeswoman last week said there are no plans to change that rule.

A spokeswoman for Delta Airlines, which requires SkyMiles members to fly on Delta at least once in three years to keep earned miles alive, said last week that the airline was studying United’s and American’s actions.

Randy Petersen, editor of Inside Flyer magazine, called the liberalization “long overdue” and said it results, in part, from the alliance boom that is pushing airlines to standardize policies with partner airlines.