Southwest Airlines is officially flying from Atlanta. The carrier’s first commercial passenger flights took off from Hartsfield-Jackson International early Sunday morning, giving Southwest a presence at the world’s busiest airport for the first time.

Southwest’s arrival, of course, comes after its acquisition of AirTran, which operates its largest hub at Atlanta. Southwest is in the process of merging with AirTran, but Sunday’s flights marked the first time that Southwest-branded planes have flown paying passengers into and out of Atlanta.

Initially, Southwest is beginning its Atlanta schedule with a total of 15 daily flights offering nonstop service to Austin, Baltimore/Washington, Chicago Midway, Denver and Houston Hobby.

The initial flights out of Atlanta were on 137-seat Boeing 737-700s that left only partially full. The first three flights each left with fewer than 50 passengers. Southwest officials pointed to this time of year being a slower period for travel and the ramp up may take time.

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