Southwest® flights from Ontario/LA to St. Louis from $189

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Low fares from Ontario/LA to St. Louis

$

Ontario/LA (ONT)to

St. Louis (STL)
Depart: 08/18/2026

One-way

Basic

From
$189
Seen: 8 hrs ago

Ontario/LA (ONT)to

St. Louis (STL)
Depart: 08/19/2026

One-way

Basic

From
$189
Seen: 8 hrs ago

Ontario/LA (ONT)to

St. Louis (STL)
Depart: 10/01/2026

One-way

Basic

From
$196
Seen: 13 hrs ago

Ontario/LA (ONT)to

St. Louis (STL)
Depart: 11/05/2026

One-way

Basic

From
$196
Seen: 5 hrs ago

Ontario/LA (ONT)to

St. Louis (STL)
Depart: 10/28/2026

One-way

Basic

From
$196
Seen: 12 hrs ago

Ontario/LA (ONT)to

St. Louis (STL)
Depart: 10/26/2026

One-way

Basic

From
$196
Seen: 8 hrs ago

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Explore flights from Ontario/LA to St. Louis

Aug 2026
From$189*
Seen: 8 hrs ago
One Way/Basic
Sep 2026
From$196*
Seen: 16 hrs ago
One Way/Basic
Oct 2026
From$196*
Seen: 6 hrs ago
One Way/Basic
cmp-daily-histogram-bars-legend-min-price-aria-label $189
cmp-daily-histogram-bars-legend-max-price-aria-label $490
Displaying fares for August-2026
  • ONT–STL: cmp-view-offers-disclaimer. Find Offers
    01

    Sat

    AUG

  • ONT–STL, 08/02/2026: From $490
    02

    Sun

  • ONT–STL, 08/03/2026: From $372
    03

    Mon

  • ONT–STL, 08/04/2026: From $320
    04

    Tue

  • ONT–STL, 08/05/2026: From $308
    05

    Wed

  • ONT–STL, 08/06/2026: From $372
    06

    Thu

  • ONT–STL, 08/07/2026: From $372
    07

    Fri

  • ONT–STL: cmp-view-offers-disclaimer. Find Offers
    08

    Sat

  • ONT–STL, 08/09/2026: From $372
    09

    Sun

  • ONT–STL, 08/10/2026: From $372
    10

    Mon

  • ONT–STL: cmp-view-offers-disclaimer. Find Offers
    11

    Tue

  • ONT–STL: cmp-view-offers-disclaimer. Find Offers
    12

    Wed

  • ONT–STL, 08/13/2026: From $372
    13

    Thu

  • ONT–STL, 08/14/2026: From $304
    14

    Fri

  • ONT–STL: cmp-view-offers-disclaimer. Find Offers
    15

    Sat

  • ONT–STL: cmp-view-offers-disclaimer. Find Offers
    16

    Sun

  • ONT–STL, 08/17/2026: From $250
    17

    Mon

  • ONT–STL, 08/18/2026: From $189
    18

    Tue

  • ONT–STL, 08/19/2026: From $189
    19

    Wed

  • ONT–STL, 08/20/2026: From $250
    20

    Thu

  • ONT–STL, 08/21/2026: From $220
    21

    Fri

  • ONT–STL: cmp-view-offers-disclaimer. Find Offers
    22

    Sat

  • ONT–STL: cmp-view-offers-disclaimer. Find Offers
    23

    Sun

  • ONT–STL: cmp-view-offers-disclaimer. Find Offers
    24

    Mon

  • ONT–STL: cmp-view-offers-disclaimer. Find Offers
    25

    Tue

  • ONT–STL: cmp-view-offers-disclaimer. Find Offers
    26

    Wed

  • ONT–STL, 08/27/2026: From $196
    27

    Thu

  • ONT–STL, 08/28/2026: From $220
    28

    Fri

  • ONT–STL: cmp-view-offers-disclaimer. Find Offers
    29

    Sat

  • ONT–STL: cmp-view-offers-disclaimer. Find Offers
    30

    Sun

  • ONT–STL: cmp-view-offers-disclaimer. Find Offers
    31

    Mon

    • Range$189-$490

    *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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