Low-fare leader Southwest Airlines is launching a partnership with the Mexican air carrier Volaris, marking Southwest's entry south of the border.

The move by Southwest, which carries more passengers than any other airline through Houston's Hobby Airport, also is its latest tack as it positions itself to snare international market share.

Earlier this year, Southwest announced a similar deal with Canadian carrier WestJet, giving Southwest a presence in that country.

Southwest and Volaris, which was founded in 2006, said in a prepared statement that they have started a relationship that ultimately will let them offer seamless travel to a variety of destinations.

Dallas-based Southwest expects Toluca-based Volaris to begin flying to the U.S. next spring, spokeswoman Olga Romero said. That would set the stage for the two carriers to connect their routes.

Although Houston could be a Volaris destination, given its proximity to Mexico and Southwest's sizable presence at Hobby, the airport has no international flights or federal facilities to handle them.