About 13% of fares Yapta tracked from January to March of this year were eligible for a refund, Pecor says. The average voucher amount was $125 in that period.

With Yapta's service, you can register for free online, and if your particular flight drops in price, you get an email or Twitter alert. Yapta takes the change fees into account and sends alerts only when a price drop exceeds the amount of the change fee. Yapta tracks 11 U.S.-based airlines for price drops. Once you get the alert, you can contact the airline and claim a refund.

For a $19.95 fee per itinerary, you can have someone follow up with an airline for you to get the refund. Yapta in May teamed up with MasterCard to form PriceAssure, which will automatically enter your flight information when you buy the ticket with your MasterCard and start tracking it. If your flight becomes eligible for a refund, the service will deal with the airlines for you and get you a voucher.

Other fare-tracking operations include:

  • Orbitz Price Assurance. It starts tracking your itinerary after your purchase. If another customer books the same itinerary at a lower price, you will automatically get a refund of between $5 and $250 per traveler for airlines and $5 to $500 on hotel rooms. The catch is that it has to be the exact same itinerary -- the same flight numbers and dates and class and restrictions.
  • Travelocity Price and Service Guarantee. Under this program, you get a guarantee that if you find a better price for the same trip, the service will match it, refund you the difference up to $500 and give you $50 toward your next trip. But you have to do the watching. Its FareWatcher Plus service will watch when prices drop for up to 10 destinations of your choosing and send you alerts.

Help with finding lower fares

Of course, if you book a low fare to begin with, you can avoid the hassle of any refund.

Several websites can help with that. Here are a few:

  • Farecompare.com offers historical information on what prices have been for trips to various cities in the past 12 months.
  • Travelzoo and Airfarewatchdog will let you see promotions not advertised elsewhere.
  • Browser extension Invisible Hand lets you download a finder tool that automatically displays lower prices in a drop-down bar as you compare airfares.

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Just knowing that fares fluctuate wildly may reduce consumers' urge to lock in too far in advance and avoid having to worry about a change fee at all, BestFares.com's Parsons says.

He gives this example: "I wouldn't touch an airfare to Europe for January, February or March with a 10-foot pole right now. The pattern's been there every single month: We've seen price drops."

This article was reported by Marcia Frellick for CreditCards.com.