What happens if the price of your airline ticket drops after you buy it?

It's a question you might be asking given the volatility of airfares lately. Many of you paid high prices for tickets earlier this year for travel this summer or fall, only to watch fares tumble.

Worth knowing: Some airlines allow travelers with nonrefundable tickets to get a credit if the price drops. Before you get too excited, keep in mind there are strings attached.

• The lower fare has to apply to the exact same itinerary, class of service, times and dates of your original booking.

• In most cases, you need to have booked directly through the airline, not an online site such as Expedia or Orbitz.

• The airline won't call you when fares drop. It's up to you to monitor fares, then call and ask for the credit.

• The refund (unless you bought a refundable ticket) will not be in cash, but rather a voucher good for future travel within one year.

Alaska Airlines/Horizon Air, JetBlue, AirTran and Southwest offer the best deals. They charge no change fees for rebooking a ticket if the fare drops. American, Delta, United/Continental US Airways, American and Virgin charge varying change fees that might negate any savings.

Alaska/Horizon and AirTran offer a credit equal to the fare difference, good for a year, if you bought your ticket directly from the airline.

JetBlue offers a similar no-fee guarantee and extends the policy to tickets bought through Expedia or another third-party ticket seller.

Southwest allows passengers to cancel reservations anytime, with no penalty, and issues a credit to be used for travel within a year.

Virgin America charges a $75 fee for changes made online and $100 through its call center. Its policy also applies to tickets bought through third-party sellers.

Rebooking/change fees, of course, can wipe out any savings.

All the biggest carriers -- Delta, United/Continental, US Airways and American -- charge hefty change fees -- $150 for domestic flights and $150-$250 for international flights.

Worth noting: United lowers its fee to $50 if a fare drops within 30 days of booking.

Keeping track of all the information isn't easy. This is where the online-travel site Yapta.com comes in. Yapta has built a business out of keeping track of the airlines' various rules, then alerting consumers when they may be eligible for refunds.

Go to www.yapta.com to see an overview of the various refund polices, then, after you've purchased your ticket, plug in the details. Yapta will monitor your flight, then notify you if fares drop to where you're eligible for a credit, taking into account change fees.