Being familiar with the Southwest Airlines ATL Terminal will greatly improve your travel experience while you are traveling with Southwest Airlines from Hartsfield-Jackson Atlanta International Airport (ATL). Everything you need to know is covered in this extensive guide, including ground transportation options, amenities, and check-in procedures. One of the busiest airports in the world, Hartsfield-Jackson Atlanta International Airport, or ATL, is a significant hub for Southwest Airlines. Southwest flies both domestically and internationally, mainly out of Concourse C at Atlanta Airport.