• If travelers today were to convert all their miles into free travel, airlines would be liable for an estimated 27 million free trips. Realistically, many of those miles will be diverted to seating upgrades, hotel stays or even merchandise. And about a quarter of all earned miles will never be used.
• Of the 180 million distinct members of frequent-flier programs — many are members of multiple programs — only about 28% are active participants in any one year.
• American's AAdvantage program is the oldest and largest program, claiming about 54 million members
• The average active member of a frequent-flier program earns 11,364 miles per year.
• An estimated 310,000 frequent fliers have earned at least 1 million miles in their programs.
• An award trip costs an airline at least $23.93, based on the food, beverage, fuel, reservations, liability insurance and miscellaneous costs. This assumes the seat occupied would have gone unsold and the airline didn't forgo revenue from a paying passenger.

Sources: Randy Petersen, publisher of WebFlyer.com (via USA Today Column)