ONT - STL

$84 Find Cheap Flights from Ontario to St. Louis - Compare and Save

1 adult
1 adult, Economy, 0 bags

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Everything you should know

Cheapest round-trip
$156
Typical prices: $250-$452
Frontier
Sun 9/16Sun 9/23
ONT - STL • 1 stop
Cheapest one-way
$84
Typical prices: $129-$232
Frontier
Fri 9/14
ONT - STL • 1 stop
Nonstop flights
Not available
There are currently no direct flights between Ontario and St. Louis. You'll need to take a connecting flight to reach the destination.
Insights
Insights
When to travel
April
Cheapest • 27% price drop
May
Most popular
Good to know
+1
Good to know
+1
Top layover airports
Las Vegas Harry Reid Intl (LAS)
Cheapest • Avg $270 (round-trip)
Phoenix Sky Harbor Intl (PHX)
Shortest trip • 5h 30m (one-way)
Insights
Insights
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Booking Insights
Flight Deals

Cheap Flights from Ontario to St. Louis (ONT-STL)

 
Discover the best prices for you by selecting your travel dates on KAYAK.

Recent round-trip flight deals from Ontario to St. Louis

Wed, Sep 16 - Wed, Sep 23
Frontier Logo
6:15 am - 7:17 pmONT  Ontario-STL Lambert-St Louis
11h 02m1 stop Denver Intl
Frontier Logo
8:10 pm - 10:30 amSTL  Lambert-St Louis-ONT Ontario
16h 20m1 stop Denver Intl
$156Frontier
Wed, Sep 16 - Wed, Sep 23
Frontier Logo
6:15 am - 7:17 pmONT  Ontario-STL Lambert-St Louis
11h 02m1 stop Denver Intl
Frontier Logo
2:29 pm - 11:47 pmSTL  Lambert-St Louis-ONT Ontario
11h 18m2 stops Atlanta Hartsfield-Jackson Denver Intl
$175Frontier
Tue, Oct 20 - Tue, Nov 17
Multiple Airlines Logo
11:52 am - 3:24 pmONT  Ontario-STL Lambert-St Louis
25h 32m1 stop Denver Intl
Multiple Airlines Logo
7:00 am - 3:13 pmSTL  Lambert-St Louis-ONT Ontario
10h 13m1 stop Seattle/Tacoma Intl
$329Multiple Airlines
Sat, Oct 17 - Tue, Oct 20
Multiple Airlines Logo
6:15 am - 6:57 pmONT  Ontario-STL Lambert-St Louis
10h 42m1 stop Denver Intl
Multiple Airlines Logo
7:02 am - 1:16 pmSTL  Lambert-St Louis-ONT Ontario
8h 14m1 stop Seattle/Tacoma Intl
$330Multiple Airlines
Tue, Dec 1 - Tue, Dec 8
American Airlines Logo
4:25 pm - 11:49 pmONT  Ontario-STL Lambert-St Louis
5h 24m1 stop Phoenix Sky Harbor Intl
American Airlines Logo
2:28 pm - 6:10 pmSTL  Lambert-St Louis-ONT Ontario
5h 42m1 stop Phoenix Sky Harbor Intl
$357American Airlines
Tue, Sep 22 - Tue, Sep 29
Delta Logo
5:15 pm - 12:44 amONT  Ontario-STL Lambert-St Louis
5h 29m1 stop Salt Lake City
Delta Logo
6:55 pm - 11:47 pmSTL  Lambert-St Louis-ONT Ontario
6h 52m1 stop Salt Lake City
$357Delta
Tue, Sep 22 - Wed, Sep 23
Delta Logo
5:15 pm - 12:44 amONT  Ontario-STL Lambert-St Louis
5h 29m1 stop Salt Lake City
Delta Logo
6:00 am - 11:09 amSTL  Lambert-St Louis-ONT Ontario
7h 09m1 stop Atlanta Hartsfield-Jackson
$357Delta
Wed, Sep 16 - Sat, Sep 26
American Airlines Logo
1:04 pm - 11:43 pmONT  Ontario-STL Lambert-St Louis
8h 39m2 stops Phoenix Sky Harbor Intl Dallas/Fort Worth
American Airlines Logo
7:00 am - 1:25 pmSTL  Lambert-St Louis-ONT Ontario
8h 25m1 stop Dallas/Fort Worth
$372American Airlines
Tue, Nov 3 - Thu, Nov 12
Southwest Logo
8:40 am - 5:25 pmONT  Ontario-STL Lambert-St Louis
6h 45m2 stops Phoenix Sky Harbor Intl Omaha Eppley Airfield
Southwest Logo
2:45 pm - 9:55 pmSTL  Lambert-St Louis-ONT Ontario
9h 10m2 stops Austin Bergstrom Las Vegas Harry Reid Intl
$394Southwest
Wed, Oct 14 - Wed, Oct 21
Southwest Logo
10:55 am - 7:45 pmONT  Ontario-STL Lambert-St Louis
6h 50m2 stops Phoenix Sky Harbor Intl Denver Intl
Southwest Logo
2:25 pm - 8:45 pmSTL  Lambert-St Louis-ONT Ontario
8h 20m2 stops Chicago Midway Dallas Love Field
$394Southwest
Booking Insights

Price, demand and travel trends for Ontario to St. Louis flights

Use KAYAK data on prices, travel dates, airlines and seasonal trends to compare options and book flights from Ontario to St. Louis with more confidence.

How much is a round-trip flight from Ontario to St. Louis?

Round-trip flights from Ontario to St. Louis start at $156. Prices are below average for this route right now, with typical round-trip fares ranging from $250 to $452. The lowest price found in the past 5 days was $156 on Frontier.

What's the cheapest day of the week to fly from Ontario to St. Louis?

Thursday is the cheapest day of the week to fly from Ontario to St. Louis, it is 25% cheaper than the average day. Tuesday is the most expensive day with flight prices 28% higher than average. Based on deals found by KAYAK users in the last 12 months.

What is the cheapest month to fly from Ontario to St. Louis?

  • April is the cheapest month to fly from Ontario to St. Louis at $250 round-trip.
  • June ($439) and July ($393) are the most expensive months.
  • The price difference between flying in the cheapest and most expensive months is 75% on average.
This is based on KAYAK aggregated and averaged internal data over the past 12 months.

Find deals

Key details for Ontario to St. Louis flights

Low season

January

Cheapest flight

$84
Most popular time to fly and prices are also 12% lower on average.
Flight from Ontario to St. Louis

When to book flights from Ontario to St. Louis

Are your dates flexible? Find out the best times to travel from Ontario to St. Louis based on our flight data from the last year. Discover the cheapest month and even day to fly.
Estimated round-trip price

Your Ontario to St. Louis flight questions, answered

Find helpful route details based on KAYAK data, including flight times, airports, airlines and booking questions.

  • Which airports can I use when flying from Ontario to St. Louis?

    Flights from Ontario to St. Louis usually depart from Ontario (ONT) and arrive at Lambert-St Louis (STL).

  • What cabin classes can I book on flights from Ontario to St. Louis?

    Two cabin classes are available on flights from Ontario to St. Louis:

    • Economy Class
    • First Class

  • Which airports do connecting flights from Ontario to St. Louis pass through?

    One-stop flights from Ontario to St. Louis most commonly connect through:

    • Denver Intl (DEN) - 40% of one-stop connections
    • Las Vegas Harry Reid Intl (LAS) - 21% of one-stop connections
    • Phoenix Sky Harbor Intl (PHX) - 18% of one-stop connections
    • Dallas/Fort Worth (DFW) - 13% of one-stop connections

    Denver Intl (DEN) handles the largest share of one-stop connections on this route.

  • Can I save money by using flexible dates for flights from Ontario to St. Louis?

    Yes. Being flexible with your travel dates can save you up to 42% on the Ontario to St. Louis route. Thursday is the cheapest departure day at $258 round-trip on average, while Tuesday is the most expensive at $438, a difference of $180. KAYAK's flexible dates feature shows options up to 3 days before and after your selected dates, making it easier to compare nearby fares.

  • What popular places can I visit in St. Louis?

    Some of the most popular sights in St. Louis are Downtown St. Louis, Busch Stadium and Enterprise Center. These are among the most viewed places in St. Louis on KAYAK.

  • How long is a flight from Ontario to St. Louis?

    A nonstop flight from Ontario to St. Louis takes 0h 00m, covering 1,541 miles.

  • Do I need a passport to fly from Ontario to St. Louis?

    No, a passport is not required for this domestic route, but you will need a real ID-compliant driver's license, a state ID, or another TSA-accepted form of identification.

  • Have flight prices from Ontario to St. Louis changed much recently?

    Yes. Based on fares seen in the past 5 days, round-trip prices on this route showed a wide range, from about $183 to $1,578. That means the highest observed fare was about 9x higher than the lowest one.

  • How are flight prices from Ontario to St. Louis looking right now?

    One-way fares from Ontario to St. Louis are currently higher than usual. Average one-way flight prices are about $173, which is 8% above the typical average for this route.

  • How much time can I save by choosing a different layover airport from Ontario to St. Louis?

    Flying via Phoenix Sky Harbor Intl (PHX) gives the shortest average 1-stop total travel time at 5h 30m, compared with 5h 39m via Austin Bergstrom (AUS) and 5h 55m via Salt Lake City (SLC).

  • What is the time difference between Ontario and St. Louis?

    St. Louis is 2 hours ahead of Ontario (Central Time vs Pacific Time). Plan for the time shift when scheduling connections or first-day activities.

  • What car rental options are available at Lambert-St Louis Airport (STL)?

    Lambert-St Louis Airport (STL) hosts 5 major car rental companies, with daily rates starting from around $31 for economy cars. Top options include:
    · Hertz
    · Budget
    · Alamo
    · Enterprise Rent-A-Car
    · Payless

  • How much should I expect to pay for a Ontario to St. Louis flight?

    Round-trip flights from Ontario to St. Louis range from $250 to $452, with an average of $340 over the past 12 months. Anything below $250 counts as a good deal.

Your guide to booking Ontario to St. Louis flights

Get tips on when to book, when to fly and what to know before your trip.
  • If your dates can be flexible, aim for a Thursday departure instead of Tuesday. On this route, Thursday flights average $258 - about $180 less than Tuesday (41% savings) based on the last 12 months.
  • If you can choose when to travel, plan your Ontario to St. Louis trip for April. Fares historically average $250 round-trip in that month - typically $189 less than the most expensive month, which is June (based on the last 12 months).
  • If you're arriving late at night and need somewhere to stay, check out these hotels close to Lambert-St Louis Airport.
    - MainStay Suites St. Louis Airport
    - Renaissance St. Louis Airport Hotel
    - Drury Inn & Suites St. Louis Airport

Everything you need to know for your flight from Ontario to St. Louis

Information on your arrival and departure airports

Ontario (ONT)
St. Louis (STL)