The Southwest Terminal Ontario, located in Ontario International Airport, is a state-of-the-art facility that caters to passengers flying with Southwest Airlines. Southwest Airlines uses Terminal 4 at Ontario International Airport (ONT).

Southwest Airlines uses Terminal 4 at Ontario International Airport (ONT). Check-in counters are located between gates 10 and 12, baggage claim is at baggage carousels 1-4, and there is a customer service desk near gate 10. Southwest Airlines does not have a dedicated lounge at Ontario Airport, but there are several third-party lounges that you can access with a membership or a paid day pass.