Who will cheer loudest when frequent-flyer miles celebrate their 25th birthday? THE mania began in 1981, when American Airlines launched AAdvantage, the world's first mileage-based frequent-flyer programme, to encourage customer loyalty. Today more than 130 airlines issue miles, and according to Randy Petersen, the founder of InsideFlyer magazine, 163m people around the globe collect miles of some sort. Indeed, calculations by The Economist in January 2005 suggested that the total stock of unredeemed miles was worth more than all the dollar bills in circulation. The record for the biggest individual account is 25m miles (enough to fly from London to...