The integration of AirTran into merger partner Southwest continues as Southwest announced it will take over nonstop service from four AirTran cities, namely Charlotte; Flint; Portland, Maine; and Rochester, beginning April 14.

The switchover means, among other things, that first and second-checked bags will begin  flying without fees from those cities in April 2013 because AirTran charges fees for those bags and Southwest doesn’t.

New Southwest cities go on sale

Starting April 14, Southwest will fly between Charlotte and Baltimore/Washington, Chicago (MDW), Houston (HOU) and Orlando; Flint, Michigan, and Baltimore/Washington, Orlando, and Tampa Bay; Portland, Maine, and Baltimore/Washington, and Rochester and Baltimore/Washington, Chicago, Orlando and Tampa Bay.

To mark the conversion of AirTran routes into Southwest schedules for these cities, Southwest kicked off a fare sale through Sunday, October 28, when booked on Southwest.com and its business travel site, Swabiz.com. One-way fares from April 14, 2013, to May 22, 2013, with most Sundays excluded, are being offered for $69 to $159.

On the international front, Southwest announced that AirTran will begin daily service between Punta Cana, Dominican Republic, and Baltimore/Washington on April 14, 2013, if  government approval materializes.

Southwest itself doesn’t currently fly to international destinations, but the airline is working on that capability, pending government approvals, as well as new reservation and revenue management functionalities.