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Cheap flights from Ontario to St. Louis from C$ 261

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 16/9. Fares are subject to change and may not be available on all flights or dates of travel.
YYZ — STL
4 Sep — 11 Sep1
1 adult
1 adult, Economy, 0 bags

Cheap flight deals from Ontario to St. Louis

Enter your travel dates to find the best prices.

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 5 August 2026.

Tue 8/91:15 p.m. -
1 stop11h 59m
Fri 11/95:00 a.m. -
1 stop8h 32m
Deal found 31/7C$ 465
Sun 8/116:30 a.m. -
1 stop14h 09m
Mon 9/1110:35 a.m. -
2 stops30h 05m
Deal found 31/7C$ 474
Sat 5/911:39 a.m. -
1 stop8h 18m
Sat 19/95:00 a.m. -
1 stop8h 32m
Deal found 4/8C$ 485
Mon 14/96:30 a.m. -
1 stop11h 18m
Mon 21/97:21 a.m. -
1 stop10h 14m
Deal found 31/7C$ 491
Thu 10/911:40 a.m. -
1 stop10h 04m
Mon 14/97:21 a.m. -
1 stop10h 14m
Deal found 3/8C$ 496
Fri 11/96:30 a.m. -
1 stop7h 46m
Tue 15/95:00 a.m. -
1 stop8h 32m
Deal found 4/8C$ 498
Thu 17/93:13 p.m. -
1 stop10h 14m
Thu 24/95:00 a.m. -
1 stop8h 32m
Deal found 3/8C$ 513
Thu 15/1012:30 p.m. -
1 stop9h 38m
Mon 19/105:27 p.m. -
1 stop17h 17m
Deal found 31/7C$ 644
Sat 22/810:00 a.m. -
1 stop5h 04m
Fri 28/88:55 a.m. -
1 stop5h 15m
Deal found 1/8C$ 647
Tue 1/95:34 p.m. -
1 stop15h 50m
Sat 5/98:06 p.m. -
1 stop14h 37m
Deal found 4/8C$ 649
Fri 28/85:34 p.m. -
1 stop15h 50m
Mon 31/86:00 a.m. -
1 stop9h 50m
Deal found 2/8C$ 654
Fri 30/108:00 a.m. -
1 stop12h 39m
Sun 1/1110:35 a.m. -
2 stops29h 09m
Deal found 31/7C$ 658

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 5 August 2026.

Round-trip from

C$ 465

One-way from

C$ 261

Popular in

March

Cheapest in

January

Average price

C$ 637

Good round-trip deal

C$ 647 or less
American Airlines
  • American Airlines
  • 8/9-11/9
  • 2 total stops
  • 20h 31m total
  • Ontario to St. Louis
Search Deals
American Airlines
  • American Airlines
  • 16/9
  • 1 total stop
  • 12h 12m total
  • Ontario to St. Louis
Search Deals
Highest demand for flights based on searches. 18% potential increase in price (C$ 236 potential increase over avg. RT price).
Search Deals
Cheapest flight prices on average. 7% potential price decrease (C$ 73 potential savings vs. average RT price).
Search Deals
Average for round-trip flights in August 2026
Search Deals
Price to beat on a round-trip flight from Ontario to Lambert-St Louis.
Search Deals

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 629,999 searches. Data last updated 5 August 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 1/12

6:15 a.m.-9:13 p.m.

1 stop15h 58m

Lambert-St Louis

Wed 2/12

6:30 a.m.-1:26 p.m.

1 stop5h 56m

C$ 662

OttawaSt. Louis

YOW - STL

YOWSTL

Ottawa

Sat 19/9

6:00 a.m.-3:38 p.m.

3 stops10h 38m

Lambert-St Louis

Wed 23/9

12:59 p.m.-9:35 p.m.

1 stop7h 36m

C$ 663
Quickest round-trip

TorontoSt. Louis

YYZ - STL

YYZSTL

Toronto Pearson Intl

Mon 14/9

12:55 p.m.-2:00 p.m.

Nonstop2h 05m

Lambert-St Louis

Mon 21/9

2:40 p.m.-5:34 p.m.

Nonstop1h 54m

C$ 665

OttawaSt. Louis

YOW - STL

YOWSTL

Ottawa

Thu 27/8

6:00 a.m.-3:38 p.m.

3 stops10h 38m

Lambert-St Louis

Thu 3/9

7:25 a.m.-5:16 p.m.

1 stop8h 51m

C$ 670

OttawaSt. Louis

YOW - STL

YOWSTL

Ottawa

Fri 30/10

6:15 a.m.-12:10 p.m.

1 stop6h 55m

Lambert-St Louis

Sun 1/11

7:30 a.m.-2:09 p.m.

1 stop5h 39m

C$ 672

TorontoSt. Louis

YYZ - STL

YYZSTL

Toronto Pearson Intl

Fri 28/8

2:00 p.m.-6:42 p.m.

1 stop5h 42m

Lambert-St Louis

Sun 30/8

8:55 a.m.-11:56 a.m.

Nonstop2h 01m

C$ 676

TorontoSt. Louis

YYZ - STL

YYZSTL

Toronto Pearson Intl

Tue 22/9

8:05 a.m.-3:38 p.m.

1 stop8h 33m

Lambert-St Louis

Sat 26/9

8:00 a.m.-5:01 p.m.

1 stop8h 01m

C$ 677

TorontoSt. Louis

YYZ - STL

YYZSTL

Toronto Pearson Intl

Sat 22/8

5:24 p.m.-10:00 p.m.

1 stop5h 36m

Lambert-St Louis

Sun 23/8

8:55 a.m.-11:56 a.m.

Nonstop2h 01m

C$ 680

TorontoSt. Louis

YYZ - STL

YYZSTL

Toronto Pearson Intl

Tue 20/10

8:50 a.m.-12:13 p.m.

1 stop4h 23m

Lambert-St Louis

Fri 23/10

8:55 a.m.-11:49 a.m.

Nonstop1h 54m

C$ 686

TorontoSt. Louis

YYZ - STL

YYZSTL

Toronto Pearson Intl

Thu 27/8

6:10 a.m.-9:37 a.m.

1 stop4h 27m

Lambert-St Louis

Sun 30/8

6:30 a.m.-11:19 a.m.

1 stop3h 49m

C$ 689

Flights are sorted by cheapest round-trip flights first.

Deals found on 30/7

Showing 1-10 of 43 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 C$ 588). Flying from Region of Ontario to St. Louis in April is currently the most expensive (average of C$ 811). 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 5 August 2026.

It’s optimal to fly from Region of Ontario to St. Louis at noon. By choosing this option you can save up to 26% on the cost of your flight, compared to a flight in the afternoon.

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 5 August 2026.

The most flights from CAON to STL are scheduled on a Monday (4 on average). You will have fewer flight options on Tuesday, which is when the least amount of flights are scheduled (2 on average).

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 C$ 631 and C$ 891 in September.
The cheapest round-trip price found within the last 5 days was C$ 465 on American Airlines (8 Sep-11 Sep).

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

To ensure you get the cheapest price possible for a flight from Region of Ontario to St. Louis, you should look to book at least 48 days in advance of your intended travel date. The price of your flight may increase if you delay and leave booking until a week or so before departure.

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?

    Most people fly into Lambert-St Louis (STL) if they book a flight to St. Louis from Ontario. Lambert-St Louis is conveniently located just 20.4 km from St. Louis’s city centre.

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

    United Airlines and Air Canada can get you from Region of Ontario to St. Louis in just under 2h 05m. Your travel time can differ by up to 13h 53m. The distance between Region of Ontario and St. Louis is about 1051 km. When browsing for deals, the options you’ll see will be for both direct 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?

    Consider Jazz (77%), Air Canada (77%) or United Airlines (65%) when booking your flight. These represent the most reliable airlines when flying from Region of Ontario to St. Louis.

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

    Looking for the cheapest flight from Region of Ontario to St. Louis? While on average our users pay C$ 754, our data indicates the cheapest price to be C$ 630. The most popular route (Toronto Pearson Intl - Lambert-St Louis), is priced around C$ 498.

  • 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 C$ 588). Flying from Region of Ontario to St. Louis in April is currently the most expensive (average of C$ 811). 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

Travelling to a place near St. Louis?

Book flights to St. Louis if you plan to visit one of these locations
Chesterfield

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Top 3 airlines flying from Ontario to St. Louis

Discover the top 3 airlines 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 629,999 searches. Data last updated 5 August 2026.
AirlineCheapestAverageFlexibilityOn-time
Air CanadaCheapestC$ 338AverageC$ 679FlexibilityNo cancel feeOn-time67%
Search Air Canada flights
United AirlinesCheapestC$ 344AverageC$ 642FlexibilityNo cancel feeOn-time69%
Search United Airlines flights
American AirlinesCheapestC$ 371AverageC$ 697FlexibilityNo cancel feeOn-time71%
Search American Airlines flights

Fly with Cheapflights

Find the best flight deals on Cheapflights, where travelers can enjoy low prices and a wide availability of flights to their desired destinations.

How does Cheapflights help users find flights from Ontario to St. Louis?

When you search for this flight from Ontario to St. Louis, Cheapflights searches on 900+ travel sites to save you time finding great flight deals online. Additionally, we offer filter features so you can choose a preferred cabin class or airline, see different price ranges, and much more so you can book the flight for you.

Why should you use Cheapflights to find cheap flight tickets from Ontario to St. Louis?

Cheapflights helps you find that perfect flight to St. Louis from Ontario by searching from hundreds of airlines and agencies you know and love. We are also free to use, in case you were wondering!

Can Cheapflights find flights from Ontario to St. Louis with no change fees?

Certainly. Search results for flights to St. Louis from Ontario shown to you on Cheapflights can be narrowed down with different useful search filters, which includes flexible booking options.

Can Cheapflights notify me if prices for flights from Ontario to St. Louis become cheaper?

Yes! Start tracking prices for Ontario to St. Louis flights today and get alerted whenever prices for these flights change. To access this feature, click the bell icon next to the flight deals above, which will prompt you for a valid email address to receive your alerts.

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