If you're wondering, What Terminal is United Airlines at ATL, United Airlines operates from the Domestic Terminal – South Area (Terminal S) at Hartsfield-Jackson Atlanta International Airport (ATL). Passengers can complete check-in, baggage drop, and security screening in the South Terminal before heading to their departure gate. Since gate assignments may change, it's always recommended to check your flight status before arriving at the airport. Arriving early ensures a smooth and stress-free travel experience.