ASIA
The largest low-cost carrier, AirAsia, now covers 65 cities in 18 countries. This year, its long-haul division, AirAsia X, began service from Kuala Lumpur to London (with one-way initial fares as low as $250). The U.S. could be next (with likely service to LAX and JFK), though negotiations are still under way. .
AUSTRALIA
Sir Richard Branson's V Australia launched in February with service from L.A to Sydney. Since then, V Australia has begun carrying passengers from LAX to Brisbane and Melbourne for rates as low as $359 each way, forcing Qantas into a fare war. .
CANADA
By year's end, Canada's low-fare pioneer, WestJet, will have grown to 66 destinations in 11 North American and Caribbean countries. New U.S. routes include Las Vegas-Montreal (from $172 one way), Miami-Toronto (from $136), and Phoenix-Vancouver (from $141). westjet.com.
HUNGARY
Budapest-based Wizz Air, launched in 2004, is emerging as the EasyJet of the East. The airline now flies more than 150 routes in Europe. It rolled out dozens of new ones this year alone, including Bucharest-Rome, Prague-London, and Budapest-Düsseldorf—all of which start at $25 one way. wizzair.com.
MEXICO
This summer, Mexico City-based Volaris began nonstop service from L.A. and Oakland to Mexico City and Guadalajara for as little as $140 each way. The 3-year-old airline also connects to vacation spots like Cancún—and plans to enter a code-sharing agreement with Southwest Airlines in 2010. volaris.com.mx.
Quick tip! You won't find these airlines on the big search sites like kayak.com; go directly to the companies' Web sites or try dohop.com, which aggregates fares for low-cost carriers worldwide.