American Airlines and merger partner US Airways will combine their frequent-flier programs "within the next 30 days," American said in an e-mail Friday to US Airways Dividend Miles and American AAdvantage members.

A specific date was not given.

US Airways earned travel miles will be transferred into an AAdvantage account. The email assured customers that they would not lose any of their miles when the programs are combined.

"Dividend Miles award bookings and mileage upgrade requests will be disabled a few days before we combine programs to allow us to integrate your accounts," American said.

For the most frequent fliers in so-called elite tiers, "your elite benefits will initially work differently for American and US Airways flights, as we'll still operate as two separate airlines," the letter said. "We'll adopt the American upgrade process for all flights when we have a single reservation system later this year."

After the programs are combined, Dividend Miles Silver, Gold, Platinum and Chairman's Preferred members will receive 500-mile upgrades to use on American flights. "We'll be providing you with more information on timing in the next few weeks," American said.