Southwest Airlines operates out of Terminal 4 at Ontario International Airport (ONT), one of the two main terminals serving passengers at this Southern California airport.Southwest Airlines ONT Terminal  is dedicated to domestic flights and provides a convenient and traveler-friendly experience tailored to Southwest’s efficient service model.Upon arrival at Terminal 4, passengers will find clearly marked check-in counters for Southwest Airlines near the main entrance. Travelers can use staffed counters or self-service kiosks to check in and drop off checked bags. For a smoother experience, mobile check-in is also available through the Southwest app, allowing you to skip the lines.
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