The airline said Thursday that it will fly to Belize from Houston beginning next October.
Southwest said that it also plans to fly to four destinations in Mexico — Mexico City, Cancun, Puerto Vallarta and Los Cabos — and to San Jose, Costa Rica, from a new international concourse being built at Houston's Hobby Airport. Southwest needs federal government approval for the flights.
The plan puts Southwest in head-to-head competition with United Airlines, which flies to all those locations from Houston's larger airport, Bush Intercontinental. Low-fare rival Spirit Airlines has announced that it will begin flying several of the same routes in May.
Southwest has taken over flights to Mexico and the Caribbean that were operated by AirTran Airways, which Southwest bought in 2011 and is now shutting down. AirTran's last flight will be Dec. 28. International flights represent only about 1 percent of Southwest's operation, far less than at United, Delta and American.
Shares of Southwest Airlines Co. were up 67 cents to $42.15 in afternoon trading Thursday. They have doubled this year.