Southwest® flights from Ontario/LA to St. Louis from $129

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Low fares from Ontario/LA to St. Louis

$

Ontario/LA (ONT)to

St. Louis (STL)
Depart: 03/04/2026

One-way

Basic

From
$129
Seen: 23 hrs ago

Ontario/LA (ONT)to

St. Louis (STL)
Depart: 03/31/2026

One-way

Basic

From
$139
Seen: 10 minutes ago

Ontario/LA (ONT)to

St. Louis (STL)
Depart: 02/24/2026

One-way

Basic

From
$139
Seen: 33 minutes ago

Ontario/LA (ONT)to

St. Louis (STL)
Depart: 05/06/2026

One-way

Basic

From
$139
Seen: 14 hrs ago

Ontario/LA (ONT)to

St. Louis (STL)
Depart: 02/26/2026

One-way

Basic

From
$147
Seen: 20 hrs ago

Ontario/LA (ONT)to

St. Louis (STL)
Depart: 02/28/2026

One-way

Basic

From
$147
Seen: 15 hrs ago

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Explore flights from Ontario/LA to St. Louis

*Fares displayed have been collected within the last 24 hours and may no longer be available at time of booking. Additional fees and charges for optional products and services may apply. Modifying this information may result in a different fare. To find the most updated fare, please visit Southwest.com. Fares listed are Basic, which are subject to additional terms and conditions.

Flight Details

Departing from:
LA/Ontario International Airport
Arriving at:
Lambert-St Louis Int'l Airport
Distance:
1546 miles

Route Information

152† Weekly flights

† Weekly flights based on DOT published scheduled average flights Monday through Sunday between 9/1/2025 and 9/30/2025. Note: route may not operate every day of the week.

‡ Nonstop flights based on DOT published scheduled average flights Monday through Sunday between 9/1/2025 and 9/30/2025.

Questions we hear the most

There are 152 weekly flights from Ontario/LA to St. Louis on Southwest Airlines.
To find the lowest fares by day and time to fly Ontario/LA to St. Louis with Southwest, check out our Low Fare Calendar.
You can rent a car at Lambert-St Louis Int'l Airport book yours with your flight.
Yes! Flights from Ontario/LA to St. Louis—or from here or there to anywhere—can be changed with no change fees. Fare difference may apply.
Check the status of your upcoming Southwest flight.
Check out the Southwest Airlines® Help Center for answers about everything Southwest.

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