None of them include Southwest's fares, however, or fares on the smaller but growing Allegiant Airlines.

CNN: The skinny on finding airfare deals

And check out AllegiantAir.com to see if Allegiant Airlines flies where you're headed, since it, too, sells tickets only on its own website.

CNN: The skinny on finding airfare deals

Spirit airlines (joined with Allegiant and Southwest airlines) challenged the regulation, which had been upheld in the U.S. Court of Appeals last July.

FORBES: In the Face of All These Mergers, Will Airline Fares Become Unfair? And Will The Consumer Even Know?