Q. I recently booked a flight on Southwest Airlines and almost immediately discovered, through an emailed alert from Airfarewatchdog.com, that the fare had gone down. Can I take advantage of the cheaper fare and get a refund?

A. You may be in luck. Southwest Airlines is one of the three U.S.-based airlines that will give you a full refund in the form of a travel voucher, good for up to a year, when a fare drops between the time you buy and the time you fly. (The other airlines are JetBlue and Alaska; other airlines will give you a refund but deduct up to $150 on a domestic fare or up to $250 on an international one, from any refund they issue, which often wipes out any value). The only caveat is that the lower fare must be available on the exact same flight times and dates as your original itinerary. You can call Southwest to get a refund. A website called Yapta.com will actually track fare drops for you, although the site doesn’t work with all airlines; most notably, Southwest Airlines is excluded.