Southwest Airlines Co. is playing up Tuesday as a huge day for the low-cost carrier’s future, when it inaugurates its first-ever international flights, though it technically inherited the Caribbean flights more than thee years ago.

Southwest’s first international flight departs BWI/Marshall Airport on Tuesday morning for Aruba, Jamaica and the Bahamas.

The flights were previously operated by AirTran Holdings Inc., acquired by Southwest in May 2011 for $1.4 billion.

Southwest will assume operations for several other AirTran-branded international flights by the end of the year, including service from BWI to Mexico and the Dominican Republic.

Southwest (NYSE: LUV) remains BWI’s largest carrier.

Southwest began flights from BWI in 1993 with 10 flights to just two cities, Chicago and Cleveland. It now operates 210 flights daily from BWI to 57 cities.

While BWI’s flights remain dominated by domestic destinations, its international passenger traffic has grown by 20 percent in each of the last two years and has nearly doubled over the last five years.