Most consumers don't realize this, but when they buy a nonrefundable airline ticket for $400 and discover before departure that the fare has gone down to, say, $200, some airlines will refund the difference in full, in the form of a voucher good for future travel, upon request. But others will deduct a fee from the refund, ranging from $25 to $100 for a domestic ticket.

Most consumers don't realize this, but when they buy a nonrefundable airline ticket for $400 and discover before departure that the fare has gone down to, say, $200, some airlines will refund the difference in full, in the form of a voucher good for future travel, upon request. But others will deduct a fee from the refund, ranging from $25 to $100 for a domestic ticket.

• Once you buy a ticket, it's a good idea to check to see if the price has gone down before you take off.
• Airlines can adjust fares up to three times a day during the week, and once a day on weekends.
• Airfare alerts such as those provided by airfarewatchdog.com are a good way to keep on top of changing airfares. These alerts are provided by email and by RSS feeds.
• If you want to get a full refund, in the form of a voucher, book with Southwest, United, USAir, or JetBlue.
• Southwest refunds in cash, the others in vouchers.
• Northwest, however, charges a $25 administrative fee on domestic fares; Continental, American, Delta charge $50-$100.
• Even those airlines that charge the fee can sometimes be persuaded to waive it. Ask nicely!
• Only caveat: you cannot change your dates or times of travel; must be exact same flights to get the refund.
• International airlines, such as British Airways, often won't refund a dime, fee or no fee. So you're better off buying your international travel with an airline like United or US Air if possible.