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St. Louis

$186+ 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 9/16. Fares are subject to change and may not be available on all flights or dates of travel.
YYZ — STL
Aug 29 — Sep 51
Sat 8/29
Sat 9/5
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 July 30, 2026.

This American Airlines deal was found by Cheapflights users on 7/30. 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.
Sat 10/177:29 am
YYZ
-
STL
1 stop10h 14m
American Airlines
Mon 10/265:00 am
STL
-
YYZ
1 stop8h 33m
American Airlines
Deal found 7/30$313
This American Airlines deal was found by Cheapflights users on 7/26. 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.
Mon 9/143:13 pm
YYZ
-
STL
1 stop10h 14m
American Airlines
Mon 9/217:21 am
STL
-
YYZ
1 stop10h 14m
American Airlines
Deal found 7/26$324
This American Airlines deal was found by Cheapflights users on 7/26. 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.
Tue 9/81:15 pm
YYZ
-
STL
1 stop11h 59m
American Airlines
Fri 9/115:00 am
STL
-
YYZ
1 stop8h 32m
American Airlines
Deal found 7/26$329
This American Airlines deal was found by Cheapflights users on 7/30. 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 9/173:13 pm
YYZ
-
STL
1 stop10h 14m
American Airlines
Mon 9/217:21 am
STL
-
YYZ
1 stop10h 14m
American Airlines
Deal found 7/30$331
This American Airlines deal was found by Cheapflights users on 7/26. 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 9/106:30 am
YYZ
-
STL
1 stop7h 46m
American Airlines
Thu 9/175:00 am
STL
-
YYZ
1 stop8h 32m
American Airlines
Deal found 7/26$334
This American Airlines deal was found by Cheapflights users on 7/28. 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.
Tue 8/253:14 pm
YYZ
-
STL
1 stop10h 00m
American Airlines
Tue 9/16:00 am
STL
-
YYZ
1 stop7h 33m
American Airlines
Deal found 7/28$354
This American Airlines deal was found by Cheapflights users on 7/30. 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 8/203:14 pm
YYZ
-
STL
1 stop10h 00m
American Airlines
Tue 8/259:32 am
STL
-
YYZ
1 stop7h 58m
American Airlines
Deal found 7/30$365
This American Airlines deal was found by Cheapflights users on 7/27. 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.
Mon 8/171:15 pm
YYZ
-
STL
1 stop11h 59m
American Airlines
Wed 8/196:00 am
STL
-
YYZ
1 stop7h 33m
American Airlines
Deal found 7/27$373
This American Airlines deal was found by Cheapflights users on 7/29. 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 8/263:14 pm
YYZ
-
STL
1 stop10h 00m
American Airlines
Sat 8/295:00 am
STL
-
YYZ
1 stop8h 33m
American Airlines
Deal found 7/29$374
This American Airlines deal was found by Cheapflights users on 7/30. 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.
Fri 11/63:15 pm
YYZ
-
STL
1 stop9h 44m
American Airlines
Mon 11/95:00 am
STL
-
YYZ
1 stop8h 33m
American Airlines
Deal found 7/30$382
This Kiwi.com deal was found by Cheapflights users on 7/29. 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 Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 9/219:50 am
YYZ
-
STL
1 stop7h 44m
Multiple Airlines
Mon 9/282:29 pm
STL
-
YYZ
2 stops25h 26m
Multiple Airlines
Deal found 7/29$399
This American Airlines deal was found by Cheapflights users on 7/27. 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 9/212:30 pm
YUL
-
STL
1 stop12h 44m
American Airlines
Wed 9/97:26 am
STL
-
YUL
2 stops13h 16m
American Airlines
Deal found 7/27$418

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 July 30, 2026.

Round-trip from

$313
(American Airlines)

One-way from

$186
(American Airlines)

Popular in

March

Cheapest in

January

Average price

$470

Good round-trip deal

$470 or less

Good one-way deal

$298 or less
From Ontario to Lambert-St Louis
Search Deals
One-way flight from Ontario to Lambert-St Louis
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Highest demand for flights based on searches. 19% potential increase in price ($125 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 July 2026
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Price to beat on a round-trip flight from Ontario to Lambert-St Louis.
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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 July 30, 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

Tue 9/8

1:15 pm-12:14 am

1 stop11h 59m

Lambert-St Louis

Fri 9/11

5:00 am-2:32 pm

1 stop8h 32m

$329

OttawaSt. Louis

YOW - STL

YOWSTL

Ottawa

Fri 10/9

7:00 am-7:39 pm

1 stop13h 39m

Lambert-St Louis

Mon 10/12

10:35 am-11:48 pm

2 stops12h 13m

$458

OttawaSt. Louis

YOW - STL

YOWSTL

Ottawa

Sat 9/12

6:00 am-2:15 pm

2 stops9h 15m

Lambert-St Louis

Sat 9/19

1:36 pm-11:54 pm

2 stops9h 18m

$467

OttawaSt. Louis

YOW - STL

YOWSTL

Ottawa

Sat 9/19

5:57 pm-11:38 pm

1 stop6h 41m

Lambert-St Louis

Wed 9/23

8:00 am-9:35 pm

1 stop12h 35m

$467

TorontoSt. Louis

YYZ - STL

YYZSTL

Toronto Pearson Intl

Tue 9/15

8:50 am-3:38 pm

1 stop7h 48m

Lambert-St Louis

Wed 9/16

7:56 am-5:01 pm

1 stop8h 05m

$475

OttawaSt. Louis

YOW - STL

YOWSTL

Ottawa

Thu 8/27

6:00 am-3:38 pm

3 stops10h 38m

Lambert-St Louis

Thu 9/3

7:25 am-5:16 pm

1 stop8h 51m

$477

TorontoSt. Louis

YYZ - STL

YYZSTL

Toronto Pearson Intl

Thu 8/27

2:00 pm-6:42 pm

1 stop5h 42m

Lambert-St Louis

Thu 9/3

8:55 am-11:52 am

Nonstop1h 57m

$478

OttawaSt. Louis

YOW - STL

YOWSTL

Ottawa

Tue 12/1

4:36 pm-9:13 pm

1 stop5h 37m

Lambert-St Louis

Wed 12/2

7:33 am-2:09 pm

1 stop5h 36m

$496
Quickest round-trip

MontrealSt. Louis

YUL - STL

YULSTL

Montreal Pierre Elliott Trudeau Intl

Thu 10/15

4:55 pm-6:41 pm

Nonstop2h 46m

Lambert-St Louis

Mon 10/19

12:10 pm-3:41 pm

Nonstop2h 31m

$500

MontrealSt. Louis

YUL - STL

YULSTL

Montreal Pierre Elliott Trudeau Intl

Wed 9/23

6:35 am-9:38 pm

2 stops16h 03m

Lambert-St Louis

Wed 9/30

1:29 pm-7:57 am

2 stops17h 28m

$503

Flights are sorted by cheapest round-trip flights first.

Deals found on 7/30

Showing 1-10 of 36 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, January is the cheapest month in which you can book a flight from Region of Ontario to St. Louis (average of $418). Flying from Region of Ontario to St. Louis in April is currently the most expensive (average of $577). 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 July 30, 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?

Airfare is below average for this route at the moment.
Region of Ontario to St. Louis flights typically cost between $421 and $634 in October.
The cheapest round-trip price found within the last 5 days was $313 on American Airlines (Oct 17-Oct 26).

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

Booking 47 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 5h 42m. 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 cheapest airlines to fly from Region of Ontario to St. Louis one-way?

    $221 is the cheapest one-way deal found within the past few days, from American Airlines. You may also be able to find cheap deals on Air Canada and United Airlines, with prices starting from $222 and $311, respectively.

  • 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: Jazz (84%), Air Canada (83%), United Airlines (68%).

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

    The cheapest flight price from Region of Ontario to St. Louis is $286. On average you can expect to pay $401. The most popular route, (Toronto Pearson Intl - Lambert-St Louis), can usually be booked for $399.

  • 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, January is the cheapest month in which you can book a flight from Region of Ontario to St. Louis (average of $418). Flying from Region of Ontario to St. Louis in April is currently the most expensive (average of $577). 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
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 July 30, 2026.
AirlineCheapestAverageFlexibilityOn-time
Air CanadaCheapest$256Average$432FlexibilityNo cancel feeOn-time67%

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