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St. Louis

$191+ Cheap flights from Ontario to St. Louis (STL)

This is the cheapest one-way flight price found by a Cheapflights user in the last 72 hours by searching for a flight departing on 7/8. Fares are subject to change and may not be available on all flights or dates of travel.
YYZ — STL
Jul 17 — Jul 241
Fri 7/17
Fri 7/24
1 adult, Economy
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Cheap flight deals from Ontario to St. Louis

Cheapest flights from Ontario to St. Louis
Explore the most affordable flight options available from Ontario to St. Louis. Find the lowest fares from popular airlines and budget airlines, with prices last updated on June 17, 2026.

This American Airlines deal was found by Cheapflights users on 6/16. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure American Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 9/93:13 pm
YYZ
-
STL
1 stop10h 14m
American Airlines
Tue 9/225:00 am
STL
-
YYZ
1 stop8h 32m
American Airlines
Deal found 6/16$310
This American Airlines deal was found by Cheapflights users on 6/14. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure American Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 7/157:17 am
YYZ
-
STL
1 stop7h 36m
American Airlines
Wed 7/226:55 am
STL
-
YYZ
1 stop9h 39m
American Airlines
Deal found 6/14$324
This American Airlines deal was found by Cheapflights users on 6/13. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure American Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 7/87:17 am
YYZ
-
STL
1 stop7h 36m
American Airlines
Wed 7/156:55 am
STL
-
YYZ
1 stop9h 39m
American Airlines
Deal found 6/13$335
This American Airlines deal was found by Cheapflights users on 6/14. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure American Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 7/297:17 am
YYZ
-
STL
1 stop10h 23m
American Airlines
Wed 8/56:00 am
STL
-
YYZ
1 stop7h 33m
American Airlines
Deal found 6/14$338
This United Airlines deal was found by Cheapflights users on 6/16. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 10/2711:00 am
YOW
-
STL
1 stop5h 38m
United Airlines
Wed 10/289:23 am
STL
-
YOW
1 stop6h 51m
United Airlines
Deal found 6/16$374
This United Airlines deal was found by Cheapflights users on 6/14. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 12/146:20 am
YOW
-
STL
1 stop8h 58m
United Airlines
Tue 12/156:30 am
STL
-
YOW
1 stop5h 56m
United Airlines
Deal found 6/14$375
This Air Canada deal was found by Cheapflights users on 6/13. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Air Canada is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 7/289:00 am
YOW
-
STL
1 stop6h 02m
Air Canada
Tue 8/412:10 pm
STL
-
YOW
1 stop6h 35m
Air Canada
Deal found 6/13$389
This United Airlines deal was found by Cheapflights users on 6/14. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 7/205:50 pm
YOW
-
STL
1 stop6h 54m
United Airlines
Fri 7/241:13 pm
STL
-
YOW
1 stop7h 22m
United Airlines
Deal found 6/14$390
This American Airlines deal was found by Cheapflights users on 6/16. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure American Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sun 9/276:15 am
YYZ
-
STL
1 stop5h 14m
American Airlines
Wed 9/307:21 am
STL
-
YYZ
1 stop10h 14m
American Airlines
Deal found 6/16$391
This United Airlines deal was found by Cheapflights users on 6/16. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 7/33:10 pm
YOW
-
STL
1 stop9h 34m
United Airlines
Tue 7/711:25 am
STL
-
YOW
1 stop4h 42m
United Airlines
Deal found 6/16$393
This American Airlines deal was found by Cheapflights users on 6/15. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure American Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 7/167:27 am
YYZ
-
STL
1 stop8h 23m
American Airlines
Tue 7/219:08 am
STL
-
YYZ
1 stop7h 26m
American Airlines
Deal found 6/15$408
This American Airlines deal was found by Cheapflights users on 6/15. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure American Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 8/1212:30 pm
YUL
-
STL
1 stop12h 44m
American Airlines
Tue 8/186:00 am
STL
-
YUL
1 stop9h 53m
American Airlines
Deal found 6/15$414

Find flight deals from Ontario to St. Louis

Keep the following information in mind while searching for Ontario to St. Louis flight deals. Data was last updated June 17, 2026.

Round-trip from

$310
(American Airlines)

One-way from

$191
(American Airlines)

Popular in

March

Cheapest in

January

Average price

$454

Good round-trip deal

$451 or less

Good one-way deal

$252 or less
From Ontario to Lambert-St Louis
Search Deals
One-way flight from Ontario to Lambert-St Louis
Search Deals
Highest demand for flights based on searches. 20% potential increase in price ($128 potential increase over avg. RT price).
Search Deals
Cheapest flight prices on average. 7% potential price decrease ($38 potential savings vs. average RT price).
Search Deals
Average for round-trip flights in June 2026
Search Deals
Price to beat on a round-trip flight from Ontario to Lambert-St Louis.
Search Deals
Price to beat on a one-way flight from Ontario to Lambert-St Louis.
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Cheapflights Fare Finder

 
Customize your flight search to find flights from Ontario to St. Louis that fit within your specific budget. Explore options based on user searches and filter the results based on your desired price range. Find flights that match your budget for a cost-effective journey. Over the last 7 days, Cheapflights users made 2,558,603 searches. Data last updated June 17, 2026.
Use the filters below to find and compare flights from Ontario to St. Louis that are best for you.

Fly from

Fly to

Route

Depart

Return

Price

Cheapest round-trip

TorontoSt. Louis

YYZ - STL

YYZSTL

Toronto Pearson Intl

Wed 7/15

7:17 am-1:53 pm

1 stop7h 36m

Lambert-St Louis

Wed 7/22

6:55 am-5:34 pm

1 stop9h 39m

$335

OttawaSt. Louis

YOW - STL

YOWSTL

Ottawa

Tue 10/27

11:00 am-3:38 pm

1 stop5h 38m

Lambert-St Louis

Wed 10/28

9:23 am-5:14 pm

1 stop6h 51m

$374

OttawaSt. Louis

YOW - STL

YOWSTL

Ottawa

Mon 12/14

6:20 am-2:18 pm

1 stop8h 58m

Lambert-St Louis

Tue 12/15

6:30 am-1:26 pm

1 stop5h 56m

$375

OttawaSt. Louis

YOW - STL

YOWSTL

Ottawa

Fri 7/31

5:50 pm-11:44 pm

1 stop6h 54m

Lambert-St Louis

Fri 8/7

6:00 am-9:35 pm

1 stop14h 35m

$390

OttawaSt. Louis

YOW - STL

YOWSTL

Ottawa

Mon 7/20

5:50 pm-11:44 pm

1 stop6h 54m

Lambert-St Louis

Fri 7/24

1:13 pm-9:35 pm

1 stop7h 22m

$390

OttawaSt. Louis

YOW - STL

YOWSTL

Ottawa

Fri 7/3

5:50 pm-11:44 pm

1 stop6h 54m

Lambert-St Louis

Tue 7/7

9:20 am-5:07 pm

1 stop6h 47m

$393

OttawaSt. Louis

YOW - STL

YOWSTL

Ottawa

Tue 10/27

9:55 am-3:38 pm

2 stops6h 43m

Lambert-St Louis

Wed 10/28

10:23 am-9:56 pm

2 stops10h 33m

$434
Quickest round-trip

TorontoSt. Louis

YYZ - STL

YYZSTL

Toronto Pearson Intl

Wed 9/9

6:55 pm-8:00 pm

Nonstop2h 05m

Lambert-St Louis

Tue 9/22

8:55 am-11:49 am

Nonstop1h 54m

$447

TorontoSt. Louis

YYZ - STL

YYZSTL

Toronto Pearson Intl

Thu 8/27

12:55 pm-2:02 pm

Nonstop2h 07m

Lambert-St Louis

Thu 9/3

8:55 am-11:52 am

Nonstop1h 57m

$479

MontrealSt. Louis

YUL - STL

YULSTL

Montreal Pierre Elliott Trudeau Intl

Tue 7/21

8:30 am-9:26 pm

2 stops13h 56m

Lambert-St Louis

Tue 7/28

7:05 pm-7:03 pm

1 stop22h 58m

$480

Flights are sorted by cheapest round-trip flights first.

Deals found on 6/12

Showing 1-10 of 44 resultsSorted by cheapest first
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Best time to book a flight from Ontario to St. Louis

Have a flexible travel schedule? Discover the best time to fly to St. Louis from Ontario with our price prediction graph.
Estimated round-trip price
Rates are based on past data. Find the cheapest month and day to book your flight based on your travel requirements, then search for cheap deals.

Cheapflights Insights

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

What is the cheapest month to book a flight from Region of Ontario to St. Louis?

Currently, December is the cheapest month in which you can book a flight from Region of Ontario to St. Louis (average of $168). Flying from Region of Ontario to St. Louis in April is currently the most expensive (average of $394). There are several factors that can impact the price of a flight, so comparing airlines, departure airports and flight times can provide users with more options.

What is the cheapest time of day to fly from ON to STL?

Find hourly flight availability from Ontario to St. Louis. Discover flight options and departure times throughout the day, allowing you to choose a departure time that suits your schedule. Data last updated June 17, 2026.

One of the essential ways to save on airfare from Region of Ontario to St. Louis is to remain as flexible as possible. Flights that are in the evening tend to be the most expensive. A flight in the afternoon could potentially save you up to 30% on airfare.

How much does it cost to fly round-trip from Region of Ontario to St. Louis?

How far ahead should I book a flight from Region of Ontario to St. Louis?

Booking 61 days in advance of your planned departure date is, on average, the best time to get cheap flights from Region of Ontario to St. Louis. The general trend is that the closer you book to the departure date, the more expensive your flight will be.

Related info for your journey

Find useful and relevant information for your journey from Ontario to St. Louis. Access travel guides, tips, and recommendations to enhance your travel experience. Get information about local attractions, weather, transportation options, and more.

  • What airport do you fly into for flights to St. Louis from Ontario?

    Located just 12.7 mi from the city center, Lambert-St Louis (STL) is the airport most travelers will use when flying to St. Louis from Ontario.

  • How long is the flight from Region of Ontario to St. Louis?

    Departing from Region of Ontario to St. Louis will take you 2h 05m. The distance between Region of Ontario and St. Louis is about 653 mi. When browsing for deals, the options you’ll see will be for both nonstop flights and flights with stops.

  • What are the most popular routes from Region of Ontario to St. Louis?

    While some choose either Montreal Pierre Elliott Trudeau Intl - Lambert-St Louis or Ottawa - Lambert-St Louis, Toronto Pearson Intl - Lambert-St Louis is the most popular route from Region of Ontario to St. Louis.

  • What are the most reliable airlines from Region of Ontario to St. Louis?

    Looking for the most reliable airlines to get you to your destination on time? Our data shows these are most likely to get you from Region of Ontario to St. Louis on time: Air Canada (88%), Jazz (87%), United Airlines (81%).

  • What are the cheapest flights from Region of Ontario to St. Louis?

    The cheapest flight price from Region of Ontario to St. Louis is $247. On average you can expect to pay $460. The most popular route, (Toronto Pearson Intl - Lambert-St Louis), can usually be booked for $372.

  • Can I find deals for flights from Ontario to St. Louis that include hotel bookings?

    Yes. In addition to deals on Ontario to St. Louis flights, Cheapflights offers vacation packages that include both flights and hotel.

  • How can I find direct flights from Ontario to St. Louis?

    After entering your origin and destination, apply the non-stop filter on the search result page to find direct flights from Ontario to St. Louis.

  • Can I find deals for business class flights from Ontario to St. Louis?

    Yes. Cheapflights offers flight deals from Ontario to St. Louis by cabin class. In addition to browsing deals, you can also filter by cabin class on the search results page after making a search.

  • What is the cheapest month to book a flight from Region of Ontario to St. Louis?

    Currently, December is the cheapest month in which you can book a flight from Region of Ontario to St. Louis (average of $168). Flying from Region of Ontario to St. Louis in April is currently the most expensive (average of $394). There are several factors that can impact the price of a flight, so comparing airlines, departure airports and flight times can provide users with more options.

See more FAQs

Traveling to a place near St. Louis?

Book flights to St. Louis if you plan to visit one of these locations
Edwardsville
O'Fallon
Fenton
Swansea
Fairview Heights
Eureka
Maryland Heights
Collinsville
Wentzville
Glencoe
Chesterfield
Alton
Farmington

Browse thousands of different options on Cheapflights for your next trip

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Top airline flying from Ontario to St. Louis

Discover the top airline that operate flights from Ontario to St. Louis. Compare their services, reliability, and customer satisfaction ratings to choose the airline that best suits your travel preferences and needs. Over the last 7 days, Cheapflights users made 2,558,603 searches. Data last updated June 17, 2026.
AirlineCheapestAverageFlexibilityOn-time
Air CanadaCheapest$256Average$432FlexibilityNo cancel feeOn-time67%

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