UNLESS YOU DON'T MIND getting stuck on a red-eye flight with three layovers, it will take a miracle combination of perfect timing and sheer luck to grab a seat on the flight you want using frequent-flier miles.

As airlines raise prices and cut back flights, redeeming award miles isn't getting any easier. Worse, some airlines, including Northwest, Delta and US Airways, actually plan to charge frequent fliers $25 to $100 just to use their miles. For many loyal passengers, it seems as if racking up all those miles may have been for naught.

But there's one alternative frequent fliers should consider before giving up on their well-earned miles. Two web sites, Points.com and LoyaltyMatch.com, enable frequent fliers and other rewards point holders to either trade their points for other rewards or cash them in.

On Toronto-based Points.com's site, for example, members of multiple rewards programs can exchange their frequent-flier miles and other rewards points. Someone who has 20,000 American Airlines frequent-flier miles can swap them for, say, a $100 Best Buy gift card. Or they can take their American miles to the site's Global Points Exchange, or GPX, where they can trade them for another member's Delta miles.

On Ontario-based LoyaltyMatch's site, instead of swapping miles, members swap the award merchandise they can get with their miles. So a person with thousands of United Airlines Mileage Plus points could trade them in for a Garmin GPS Navigator (259,000 points) and then post those rewards on LoyaltyMatch's site to see if another member might be interested in buying it. Once someone bites, the site facilitates the trade.

These sites may seem like more trouble than they're worth, but for a disgruntled frequent flier they offer flexibility and an avenue to take advantage of miles that may have otherwise gone unused. "Even if you don't get a particularly good value, it might still be worth it to get them out of your life," says Tim Winship, editor at large for SmarterTravel.com. After all, frequent-flier miles have been losing their value over time a trend that's far from reversing course.

But before trading in your miles for an iTunes gift card or a Samsung DVD camcorder, keep these things in mind.

Expect to Pay Fees

Neither site charges membership fees. However, Points.com's GPX charges a $6.95 processing fee for each trade. LoyaltyMatch charges $1.99 Canadian (roughly the same in U.S. dollars now) for each transaction, but for the month of August, is waiving all transaction fees.

There are other fees beyond these sites to consider, though. Each participating reward program, whether it be American Airlines' AAdvantage or Delta's SkyMiles, charges a fee when you transfer miles or points to another member. Typically, says Chris Barnard, president of Points.com, those fees come to about one cent per mile. Delta, for example, charges $30 plus one cent per mile in transfer fees. So if you transfer 20,000 miles from one account to another, the fee comes to a wallet-busting $237.

Calculate the Exchange Ratios

If it's not immediately evident, users should know that they're probably "getting a watered-down value in exchange for all that flexibility," says Ben Woolsey, director of marketing and consumer research at CreditCards.com. At Points.com some redemption options cost more miles or points than others. For instance, says Woolsey, a $100 Crutchfield gift certificate would cost 21,176 American Airlines miles, while a $100 Best Buy gift card costs 24,824 miles and two $50 iTunes gift cards would require 26,118 miles.

So before buying anything, have a basic notion of what your miles or points are worth. "Wherever you earned your miles or points, it's important to do the math and figure out exactly what you're getting when you make one of these transactions," says Winship. To help you figure it out, divide the item's cost by the number of points or miles required to buy it.

Limited Selections

Only a couple of U.S. airlines, such as Delta and United, offer their frequent-flier members the option to buy merchandise (electronics, sports equipment, etc.) with their miles. Other airlines only let members buy magazine subscriptions with their miles. So a LoyaltyMatch member who wants to unload US Airways or American Airlines miles can only offer up magazine subscriptions for exchanges. An American Express rewards member, on the other hand, has a vast catalog of retail items (like a Badgley Mischka beaded clutch), that they can "sell" on the site. "That's one of the significant limitations of LoyaltyMatch. They're assuming that many of the airline programs will in the future be offering merchandise for miles," says Winship. As he explains, that may be far from the case, especially since things are looking so dismal for the airline industry these days.

Also See:
Some Car Renters Socked With $8 a Gallon Gas
Getting Around Airlines' New Minimum-Stay Requirements
How to Avoid Hidden Hotel Fees