Not all airlines are alike when it comes to redeeming your points for a free ticket. After making 6,160 queries at 22 airline websites, the consulting firm Ideaworks found that you're much better off on Southwest than Delta and US Airways. Lots better off - Southwest fulfilled 99.3 percent of the requests for its frequent flier award seats, while US Airways was good only 10.7 percent of the time (that's partly because the airline makes award seats available closer to when flights depart). As could be expected, shorter routes garnered the most success - and that's what Southwest does. From the WSJ:
The numbers codify what a lot of fliers have suspected for some time, that some airlines are making it almost impossible to score a free trip using miles--at least without having to pay a significantly higher price in miles than the standard award. The problem is, in part, that there are just too many miles chasing too few seats. Worldwide, there are an estimated 10 trillion frequent-flier miles outstanding. And the problem of scarce seats is getting worse: The number of awards redeemed fell significantly at several big carriers--including Continental Airlines Inc. and AMR Corp.'s American Airlines--between 2008 and 2009. So did the percentage of passengers flying on awards.
If you do decide to look for an upgrade, be prepared to open your wallet. Four of the five U.S. airlines flying long-haul international trips--American, United, Continental and US Airways--have added "co-payments" to international upgrades, requiring customers to pay in miles and cash if an upgrade is available. Delta, which doesn't charge a cash fee for an upgrade, restricts the coach fare classes eligible for upgrades, forcing passengers interested in an upgrade to purchase a coach ticket often several hundred dollars more expensive than the cheapest fare available.