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Learn moreBook cheap flights from Ontario/LA to St. Louis with Southwest Airlines®. It’s easy to find the Ontario International Airport to Lambert-St. Louis International Airport flight to make your booking and travel a breeze. Whether you’re traveling for business or pleasure, solo or with the whole family, you’ll enjoy flying Southwest®. Have flexible travel dates? Plug them into the Low Fare Calendar and see the lowest fares available within your travel window. You may also want to browse Southwest Vacations® to see special offers and package deals on flights, hotels, rental cars, and more.
Explore your options and book your Ontario/LA to St. Louis flight with Southwest today!
Best Airline in the US and North America
Bags Fly Free®1
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No Change Fees2
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Free Entertainment
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Fly in Comfort
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Rapid Rewards ®
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Sips 'n Snacks
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Departing from: Ontario International Airport (ONT)
Arriving at: Lambert-St. Louis International Airport (STL)
10Daily flights |
67Weekly flights |
6Flights before noon |
4Flights between |
Other popular flights from Ontario/LA
| Chicago (MDW) | Indianapolis (IND) |
| Kansas City (MCI) | Louisville (SDF) |
One child over 14 days and under two (2) years of age, not occupying a seat, may be carried free of charge when traveling with an adult (12 years of age or older). Learn more.
Customers flying with a pet are subject to a pet fare. To learn more about traveling with your furry friend, explore the Southwest Pet Policy.
Minors under the age of 18 are not permitted to fly unaccompanied on international flights or any itinerary that includes an international flight. Learn more.
Start packing! Every ticketed Customer’s first two checked bags are free. Learn more.
Lambert-St. Louis International Airport will bring you within 14 miles of downtown St. Louis. Hop on a bus, or train, or call a car to get on your way.
At Southwest, we know it takes more than great deals on St. Louis airfares and convenient scheduling options to make your trip memorable. So from booking to boarding, we offer services and features designed to make your travel from Ontario/LA to St. Louis the best it can be. Find out more about the Southwest Experience before you book your Ontario International Airport to Lambert-St. Louis International Airport flight.
Flying with Southwest is simple and fun, no matter which of our dozens of exciting destinations you choose. And when you search for your next flight to St. Louis, you know you won’t be surprised at checkout. Low fares, no hidden fees. That’s our Transfarency® promise. And, as always, bags fly free1. Enroll in our Click 'N Save® emails and stay up to date on our latest flight deals. Looking for tours, activities, and more hidden gems to add to your St. Louis adventure? Explore Southwest Airlines® Experiences and earn Rapid Rewards® when you book.
1First and second checked bags. Weight and size limits apply.
2Fare difference may apply.