Use this global search engine to check 21 airfare sites for the best fares. This airfare search covers Airtran, American, Americawest, ATA, Alaska, Aloha, Cheapseatstravel, Delta, Continental, Frontier, Jetblue, National, Northwest, Southwest, Hawaiian, Travelnow, Singapore, USAirways, Spirit, and United. It's the best of its kind according to "Money Magazine."