How to find the best airfare

By George Hobica

updated 3:16 p.m. ET Aug. 28, 2007

When you go looking for the best airfare, there are several points you should keep in mind.

First is that there really isn't one "magic bullet" airfare Web site, even though travel techies have been trying to build one for years.

One of the problems is that low fare leader Southwest Airlines, now the largest U.S. carrier based on domestic passengers boarded, doesn't release its fares to any site other than its own.

That's also true of new low-fare airline SkyBus, and of the fast-growing low-fare carrier Allegiant Airlines. Also, those Spirit Airlines 1 cent or $1 fares, which you can sometimes actually book, only appear on Spirit's site.

When I'm booking my own domestic travel I'm usually flexible in my dates, so I start my search with Travelocity, using its flexible search option. I also like Orbitz' flexible search, which also includes flights from the United States to foreign lands.

If I'm looking for a flight between two foreign countries, I use Travelocity's Canadian affiliate, or Mobissimo.com. Caveat: You can't book travel, if you're a U.S. citizen, on Travelocity Canada, where the fares are listed in Canadian dollars. (However, the U.S. dollar is almost on par with the Canadian dollar, so you can just deduct 10 percent to get an idea what it'll cost in greenbacks.) But these sites don't include all the discount foreign airlines, such as Ryanair.

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The advantage to Kayak is that it doesn't charge a booking fee. The same is true for Sidestep.com. However, neither site includes Southwest, SkyBus, Allegiant, and some other super-low-cost airlines. And they don't include many of the international airlines' lowest discount fares, which can only be bought on the airlines' own sites.

Also, Kayak, Sidestep, and Mobissimo don't have good flexible date searches, so if you're willing to adjust your travel dates to find the best deal, these sites are not for you. The same can be said for individual airline sites: very few have a good flexible search function. American has a 31-day flexible search, but only for domestic roundtrip fares.

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Many people search on third-party sites such as Travelocity and then book the fare on the site of the airline offering the lowest fare. This does help avoid booking fees, and gets you bonus frequent flyer miles.

The only downside to this approach is that if everyone did this, the third-party sites would go out of business. You'd be killing the golden geese — and sometimes, it's just plain easier using a Travelocity or an Orbitz than it is to use an airline site.

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