Sadly, I won't be flying Frontier Airlines again soon. It's not the airline or the service. I love our cuddly local Denver carrier and its get-out-the-vote campaign to select a favorite tailfin mascot. My problem is with the miles.

Thanks for stopping short
You see, at one time, Frontier (NASDAQ:FRNT) was an affinity partner of Virgin Atlantic Airways, which meant the two would -- theoretically, at least -- help to drive revenue to each other while serving passengers with global travel ambitions.

For me, the deal meant that I could fly Frontier to Fool HQ and still earn miles on Virgin, which fit very nicely with my six-year plan. But no longer. Frontier now has a mileage-swapping deal with AirTran (NYSE:AAI), which appears to be a first step towards a broader code-sharing agreement.

Don't let your miles fly away
Here are three reasons why this matters to frequent-flier Fools:

  1. Affinity programs frequently change.
  2. Those changes are rarely announced.
  3. Changes almost always affect what you can redeem.

For example, to help keep operating costs under control, United Airlines parent UAL (NASDAQ:UAUA) recently announced that Mileage Plus accounts that have not earned or redeemed miles since last July will see their points expire Dec. 31.

Business-wise, this makes sense. Frequent-flier seats are like gift cards in retail. Though retailers get cash from every gift card sold, there's no telling when buyers will redeem them. That can make inventory management a nightmare.

Airlines don't have exactly the same problem, but if there's a glut of miles, it can create problems when planes are flying full with fare-paying passengers, as they are now. Customers who've invested in collecting points won't suffer the stiff-arm for long before they flee to carriers who make them feel more loved.

How you can respond
If you're holding United miles now and have no plans to travel before Dec. 31, you needn't watch your miles slip away. Transfer them instead. United's transfer options include:

  • Reader rewards. Enter your zip code, and you could get 13 weeks of The Wall Street Journal free. But beware the catch: You can't re-up your subscription to the Journal. By week 14, you'll be paying cash.
  • Mileage Plus Music. United has a cross-promotion deal with Sony (NYSE:SNE) whereby you can trade in 10,000 miles for 100 songs or 10 albums.
  • Dining certificates. As little as 1,000 miles will get you $25 off a meal at any of 7,000 restaurants. But here, too, you need to be aware of the catch: Restaurants are free to place restrictions on use of these certificates.

Follow the money
If none of these options leaves you feeling loved, I won't blame you. Mileage Plus has almost overnight devolved into one of the industry's worst affinity programs.

But there are other loser programs. You may be trapped in one of them. To find out, call your airline service desk and ask these three questions:

  1. For what other programs can I earn miles when I fly on your airline?
  2. Can I transfer miles into those programs? At what rate?
  3. When do my miles expire?

Another good source is the mileage converter at Its comprehensive list will help you collect and redeem orphaned miles and points so that you get more from your earning.

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Fool contributor Tim Beyers, who is ranked 2,543 out of more than 22,800 in our Motley Fool CAPS investor intelligence database, writes weekly about personal finance and investing basics. Have a Foolish money tip? Tell him.

Tim didn't own shares in any of the companies mentioned in this story at the time of publication. All of Tim's portfolio holdings can be found at his Fool profile. His thoughts on affinity programs, Foolishness, and investing in general may be found in his blog. The Motley Fool's disclosure policy prefers first class, but will settle for business class.