If an airline drops prices after you buy, you may be able to get some money back.

Have you ever bought an airline ticket only to see the price fall and your anger rise? Now there is something you can do about it.

Few customers realize it, but many airlines will give refunds if they cut the price after you have bought a ticket. Alaska, JetBlue, Southwest, United and US Airways all offer vouchers for the full price difference — if the price drops $200, you can get a $200 coupon towards a future trip. Others offer vouchers, or cash, after deducting change fees (which can run up to $100). In industry jargon, it is called a “rollover,” and in most cases it only works if you bought the ticket directly from the airline. (It generally won’t work if you bought them via a Web site such as Expedia.com or Orbitz.com, unless the price drops in the first 24 hours.)