What Terminal is Southwest at Denver Airport?Southwest Airlines operates at Terminal C of Denver International Airport (DIA). As one of the major carriers at DIA, Southwest Airlines uses Terminal C as its primary terminal for check-in, boarding, and departures. Passengers flying with Southwest Airlines can conveniently access the airline's dedicated check-in counters and enjoy the range of facilities and amenities available at Terminal C. Whether you're departing on a domestic or international flight, Terminal C at Denver Airport is the designated location for Southwest Airlines operations, providing a seamless and enjoyable travel experience for all passengers.