Southwest Airlines plans to operate Boeing 737 flights starting in late 2015 from its new Houston Hobby Airport (HOU) international terminal to four destinations in Mexico as well as San Jose, Costa Rica and Belize City, Belize.

Southwest has filed applications with the US Department of Transportation (DOT) to operate the routes from HOU. The $156 million HOU facility, slated to open in the 2015 autumn, will be the carrier’s first terminal dedicated to international flights. Southwest, which began operating branded international flights for the first time this year, currently operates to seven international destinations as well as San Juan, Puerto Rico.

None of Southwest’s current international flights retain the AirTran Airways brand, which still exists on some domestic flights but will be retired completely after Dec. 28. The Mexican destinations Southwest plans to serve from HOU are Mexico City, Cancun, Puerto Vallarta and San Jose del Cabo/Los Cabos. Southwest will begin Aruba flights from HOU in March 2015 before completion of the international terminal. This is possible because there is a US customs pre-clearance facility in Aruba.

Southwest currently operates to 93 total destinations and believes there are 50 potential destinations it could add, “virtually all of them outside the 48 states” of the continental US, chairman, president and CEO Gary Kelly told The Wings Club in New York this week.

Belize City will be the third new destination added to Southwest’s network in 2015, following San Jose, Costa Rica (which it will serve from Baltimore/Washington International Airport starting March 7) and Puerto Vallarta (which it will serve from Orange County Wayne Airport starting June 7).

Kelly said Southwest is eyeing a fourth addition to its network in 2015, but won’t announce the destination until next year. He noted that passengers flying on Southwest’s international flights are “mostly US citizens traveling for leisure.” International flying currently makes up about 1% to 1.5% of Southwest’s capacity, Kelly said.

Kelly credited Southwest’s decision to slowly rebrand AirTran flights as Southwest flights as a key to the Southwest-AirTran merger being “a tremendous success” with no major integration or operational problems. “We didn’t do a hard cutover,” he explained. “We did it gradually over a two- to three-year time period.”

The last AirTran branded 737 flights will occur on Dec. 28, after which the last 18 AirTran 737s will be temporarily taken out of service to be converted into Southwest aircraft in early 2015, Kelly said.