Some airports much cheaper than others

When you're searching for airfare bargains, it's not only the airline that matters. The airport you're leaving from can also cause your ticket price to climb.

No one knows this better than the 176,000 or so folks who call Huntsville, Ala. home. The city's international airport reported the highest average domestic airfare in the country --a whopping $491.82 for the fourth quarter of 2009, according to a list of the 100 most expensive U.S. airports recently released by the federal Bureau of Transportation Statistics.

In second place, with an average domestic airfare of $423.76, was Savannah, Ga.'s international airport, followed by Grand Rapids, Mich. in third at $412.40, Knoxville, Tenn. in fourth at $410.25, and Newark, N.J. rounding out the top five at $405.19.

The nation's most expensive airports count several things in common that keep airfares in their cities artificially high, including fewer airlines competing with one another for passengers, a sparse number of destinations to choose from, as well as a lack of alternative airports nearby.

When Southwest Airlines enters the picture, however, all bets are off. With consistently low prices, the carrier incites fare wars among rivals the minute it arrives at a new facility -- a phenomenon so common it's known as the "Southwest effect."