For years, Southwest Airlines confined its route structure to the U.S. mainland proper. Then it bought AirTran, and almost in an instant, it was a player in Mexico and the Caribbean. Now comes news the low-fare juggernaut is continuing its slow surge south, making Indianapolis its 17^th international gateway. To be sure, Indy isn’t any mega-hub, but come March 10, 2018, it will see Saturday-only nonstop service to the Mexican resort of Cancun. From March 8, 2018, Southwest adds a new route from its busy Fort Lauderdale/Hollywood, gateway to the Caribbean island of Aruba. Polishing its U.S. Midwest product, there will also be a new domestic leg between Milwaukee and Houston Hobby, a prime Latin and Caribbean connection point for Southwest to places such as Cancun, Belize and Mexico City. This new service illustrates the metered sort of expansion that’s a hallmark of the airline. JetBlue and Spirit offer a slew of service south, but Southwest’s measured approach indicates it’s in no particular hurry to be king of Caribbean.