Southwest® flights from St. Louis to Ontario/LA from $139

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Low fares from St. Louis to Ontario/LA

$

St. Louis (STL)to

Ontario/LA (ONT)
Depart: 02/24/2026

One-way

Basic

From
$139
Seen: 15 hrs ago

St. Louis (STL)to

Ontario/LA (ONT)
Depart: 02/23/2026

One-way

Basic

From
$167
Seen: 15 hrs ago

St. Louis (STL)to

Ontario/LA (ONT)
Depart: 02/28/2026

One-way

Basic

From
$167
Seen: 7 hrs ago

St. Louis (STL)to

Ontario/LA (ONT)
Depart: 02/27/2026

One-way

Basic

From
$167
Seen: 8 hrs ago

St. Louis (STL)to

Ontario/LA (ONT)
Depart: 02/26/2026

One-way

Basic

From
$167
Seen: 8 hrs ago

St. Louis (STL)to

Ontario/LA (ONT)
Depart: 03/24/2026

One-way

Basic

From
$169
Seen: 12 hrs ago

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Explore flights from St. Louis to Ontario/LA

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

Route Information

155† 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 155 weekly flights from St. Louis to Ontario/LA on Southwest Airlines.
To find the lowest fares by day and time to fly St. Louis to Ontario/LA with Southwest, check out our Low Fare Calendar.
You can rent a car at LA/Ontario International Airport book yours with your flight.
Yes! Flights from St. Louis to Ontario/LA—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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