Low-Cost Lions

Ever since Southwest invented the low-cost airline, the concept has morphed into a cottage industry within the larger airline business. Here's a rundown of key low-cost players:

Southwest Airlines: The largest low-fare operation. Especially dominant in Las Vegas, Phoenix, Baltimore, and Chicago Midway. Has the best balance sheet of any U.S. carrier.

JetBlue Airways: A distant second to Southwest in size, JetBlue nonetheless has new planes, satellite television, and a superior service record. Particularly strong routes out of New York City.

AirTran Airways: This fast-growing airline with premium-class seating is gunning for JetBlue's runner-up spot. Very strong in Atlanta and Dallas.

Frontier Airlines: Frontier's vital headquarters hub in Denver feeds strong western routes, with plenty of room for growth. Better than average in-flight entertainment.

Spirit Airlines: Big in Fort Lauderdale and Detroit, Spirit has new planes from Airbus with first-class seating. Also has some Caribbean routes.

ATA: A recent code-share deal with Southwest rescued this carrier from dire financial straits but deprived it of important gate space at Chicago Midway. An airline in transition.

USA 3000 Airlines: This fairly new low-cost operator offers remarkably low fares from its St. Petersburg, FL, headquarters, to Midwestern cities like Pittsburgh, Detroit, Cleveland, and Chicago.

Independence: Operating out of Dulles Airport in Washington D.C., this carrier uses regional jets to keep load factors high and fares low, on routes up and down the East Coast.

Sun Country Airlines: This Minneapolis-based low-cost airline has leather seats, hot meals, and a first-class cabin. Profitable service to the East and West Coasts, and Mexico.