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St. Louis

$184+ 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 4/30. Fares are subject to change and may not be available on all flights or dates of travel.
YYZ — STL
Apr 18 — Apr 251
Sat 4/18
Sat 4/25
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 March 19, 2026.

This Air Canada deal was found by Cheapflights users on 3/18. 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 5/57:00 am
YOW
-
STL
1 stop6h 06m
Air Canada
Wed 5/61:05 pm
STL
-
YOW
1 stop6h 46m
Air Canada
Deal found 3/18$299
This Air Canada deal was found by Cheapflights users on 3/18. 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.
Fri 6/57:00 am
YOW
-
STL
1 stop6h 06m
Air Canada
Sun 6/77:05 am
STL
-
YOW
1 stop5h 00m
Air Canada
Deal found 3/18$305
This United Airlines deal was found by Cheapflights users on 3/15. 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 United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 5/225:20 pm
YOW
-
STL
1 stop4h 56m
United Airlines
Sun 5/241:13 pm
STL
-
YOW
2 stops9h 41m
United Airlines
Deal found 3/15$308
This United Airlines deal was found by Cheapflights users on 3/16. 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.
Wed 6/310:44 am
YOW
-
STL
1 stop6h 02m
United Airlines
Sat 6/66:00 am
STL
-
YOW
1 stop14h 35m
United Airlines
Deal found 3/16$309
This American Airlines deal was found by Cheapflights users on 3/19. 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 4/1512:30 pm
YUL
-
STL
1 stop10h 47m
American Airlines
Tue 4/218:03 pm
STL
-
YUL
1 stop14h 41m
American Airlines
Deal found 3/19$327
This American Airlines deal was found by Cheapflights users on 3/19. 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 5/271:15 pm
YYZ
-
STL
1 stop11h 39m
American Airlines
Wed 6/101:45 pm
STL
-
YYZ
1 stop8h 44m
American Airlines
Deal found 3/19$346
This United Airlines deal was found by Cheapflights users on 3/18. 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 5/52:00 pm
YOW
-
STL
2 stops8h 13m
United Airlines
Wed 5/67:45 am
STL
-
YOW
1 stop8h 22m
United Airlines
Deal found 3/18$371
This American Airlines deal was found by Cheapflights users on 3/18. 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 4/153:13 pm
YYZ
-
STL
1 stop8h 04m
American Airlines
Wed 4/228:54 am
STL
-
YYZ
1 stop7h 49m
American Airlines
Deal found 3/18$380
This American Airlines deal was found by Cheapflights users on 3/18. 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 5/212:30 pm
YUL
-
STL
1 stop8h 39m
American Airlines
Sat 5/92:33 pm
STL
-
YUL
1 stop20h 11m
American Airlines
Deal found 3/18$393
This Kiwi.com deal was found by Cheapflights users on 3/16. 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 Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 4/135:15 pm
YYZ
-
STL
2 stops38h 35m
Multiple Airlines
Mon 4/204:59 pm
STL
-
YYZ
1 stop20h 09m
Multiple Airlines
Deal found 3/16$393
This American Airlines deal was found by Cheapflights users on 3/14. 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.
Tue 4/2812:30 pm
YUL
-
STL
1 stop12h 16m
American Airlines
Tue 5/54:30 pm
STL
-
YUL
1 stop18h 14m
American Airlines
Deal found 3/14$394
This American Airlines deal was found by Cheapflights users on 3/15. 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.
Tue 5/512:30 pm
YUL
-
STL
1 stop10h 49m
American Airlines
Sat 5/98:03 pm
STL
-
YUL
1 stop14h 41m
American Airlines
Deal found 3/15$398

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 March 19, 2026.

Round-trip from

$299
(Air Canada)

One-way from

$184
(United Airlines)

Popular in

March

Cheapest in

June

Average price

$925

Good round-trip deal

$440 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
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Highest demand for flights based on searches. 20% potential increase in price ($125 potential increase over avg. RT price).
Search Deals
Cheapest flight prices on average. 8% potential price decrease ($40 potential savings vs. average RT price).
Search Deals
Average for round-trip flights in March 2026
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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 March 19, 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

OttawaSt. Louis

YOW - STL

YOWSTL

Ottawa

Tue 5/5

7:00 am-12:06 pm

1 stop6h 06m

Lambert-St Louis

Wed 5/6

1:05 pm-8:51 pm

1 stop6h 46m

$299

OttawaSt. Louis

YOW - STL

YOWSTL

Ottawa

Fri 5/22

5:20 pm-9:16 pm

1 stop4h 56m

Lambert-St Louis

Sun 5/24

1:13 pm-9:35 pm

1 stop7h 22m

$308

OttawaSt. Louis

YOW - STL

YOWSTL

Ottawa

Wed 6/3

10:44 am-9:16 pm

1 stop11h 32m

Lambert-St Louis

Sat 6/6

9:23 am-9:35 pm

1 stop11h 12m

$308

OttawaSt. Louis

YOW - STL

YOWSTL

Ottawa

Tue 5/5

2:00 pm-9:13 pm

2 stops8h 13m

Lambert-St Louis

Wed 5/6

7:45 am-5:07 pm

1 stop8h 22m

$371

OttawaSt. Louis

YOW - STL

YOWSTL

Ottawa

Fri 6/5

5:05 am-12:11 pm

2 stops8h 06m

Lambert-St Louis

Sun 6/7

1:13 pm-9:35 pm

1 stop7h 22m

$371

MontrealSt. Louis

YUL - STL

YULSTL

Montreal Pierre Elliott Trudeau Intl

Mon 4/20

6:00 am-9:42 am

1 stop4h 42m

Lambert-St Louis

Sat 4/25

6:48 am-11:59 am

1 stop4h 11m

$460

MontrealSt. Louis

YUL - STL

YULSTL

Montreal Pierre Elliott Trudeau Intl

Wed 4/15

11:23 am-9:52 pm

2 stops11h 29m

Lambert-St Louis

Tue 4/21

6:15 am-1:09 pm

1 stop5h 54m

$460

MontrealSt. Louis

YUL - STL

YULSTL

Montreal Pierre Elliott Trudeau Intl

Wed 4/29

1:20 pm-9:13 pm

1 stop8h 53m

Lambert-St Louis

Sat 5/2

9:00 am-9:26 pm

1 stop11h 26m

$460
Quickest round-trip

TorontoSt. Louis

YYZ - STL

YYZSTL

Toronto Pearson Intl

Thu 4/16

2:10 pm-3:25 pm

Nonstop2h 15m

Lambert-St Louis

Thu 4/23

6:30 am-11:49 am

1 stop4h 19m

$487

TorontoSt. Louis

YYZ - STL

YYZSTL

Toronto Pearson Intl

Thu 6/4

7:30 am-3:46 pm

2 stops9h 16m

Lambert-St Louis

Mon 6/8

9:23 am-5:56 pm

1 stop7h 33m

$501

Flights are sorted by cheapest round-trip flights first.

Deals found on 3/16

Showing 1-10 of 46 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 $247). Flying from Region of Ontario to St. Louis in April is currently the most expensive (average of $370). 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 March 19, 2026.

Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Region of Ontario to St. Louis as you normally would.

Weekly flight availability from Region of Ontario to St. Louis

Explore weekly flight availability from Ontario to St. Louis. Discover flights operating on different days of the week, giving you the flexibility to choose a travel day that best fits your plans. Compare info to find the most convenient option for your journey. Data last updated March 19, 2026.

The most flights from CAON to STL are scheduled on a Monday (2 on average). You will have fewer flight options on Monday, which is when the least amount of flights are scheduled (2 on average).

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 4h 32m. 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?

    $187 is the cheapest one-way deal found within the past few days, from Air Canada. You may also be able to find cheap deals on United Airlines and American Airlines, with prices starting from $188 and $219, 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: United Airlines (72%), Air Canada (71%), Jazz (71%).

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

    The cheapest flight price from Region of Ontario to St. Louis is $222. On average you can expect to pay $384. The most popular route, (Toronto Pearson Intl - Lambert-St Louis), can usually be booked for $393.

  • 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 $247). Flying from Region of Ontario to St. Louis in April is currently the most expensive (average of $370). 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
Maryland Heights
Collinsville
Eureka
Wentzville
Glencoe
Chesterfield
Alton
Farmington
Festus

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 March 19, 2026.
AirlineCheapestAverageFlexibilityOn-time
Air CanadaCheapest$323Average$553FlexibilityNo cancel feeOn-time67%

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