HomeSearch by dateVacation packagesHotelsFlight dealsCar rentalTravel tips & news
Ontario

$103+ Cheap flights from St. Louis (STL) to Ontario

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 10/3. Fares are subject to change and may not be available on all flights or dates of travel.
STL — YYZ
Oct 11 — Oct 181
Sat 10/11
Sat 10/18
1 adult, Economy
We work with more than 300 partners to bring you better travel deals

Find cheap flights from St. Louis to Ontario with Cheapflights

1. Tell us where you want to go

Enter your travel information like dates, passengers, trip type (one-way or round trip), and preferred cabin class then click “Find deals”

2. Select your favorite providers

We find the providers serving your travel needs. Choose up to four travel providers to compare side-by-side for flights, hotels, or car rentals.

3. Compare prices and book

Review each provider’s pricing and select the best option for you! Book through your favorite provider’s website for a seamless experience.

Cheap flight deals from St. Louis to Ontario

Keep the following information in mind while searching for St. Louis to Ontario flight deals. Data was last updated September 11, 2025.

Round-trip from

$261
(Kiwi.com)

One-way from

$103
(Kiwi.com)

Popular in

March

Cheapest in

November

Average price

$488

Good round-trip deal

$672 or less

Good one-way deal

$349 or less
From Lambert-St Louis to Ontario
Search Deals
One-way flight from Lambert-St Louis to Ontario
Search Deals
High demand for flights, 1% potential price rise
Search Deals
Cheapest flight prices on average. 3% potential price decrease ($15 potential savings vs. average RT price).
Search Deals
Average for round-trip flights in September 2025
Search Deals
Price to beat on a round-trip flight from Lambert-St Louis to Ontario.
Search Deals
Price to beat on a one-way flight from Lambert-St Louis to Ontario.
Search Deals

Find flight deals from St. Louis to Ontario

Cheapest flights from St. Louis to Ontario
Explore the most affordable flight options available from St. Louis to Ontario. Find the lowest fares from popular airlines and budget airlines, with prices last updated on September 11, 2025.

This Kiwi.com deal was found by Cheapflights users on 9/9. 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.
Thu 10/910:57 amSTL - YYZ
1 stop11h 55mMultiple Airlines
Thu 10/161:30 pmYYZ - STL
2 stops23h 13mMultiple Airlines
Deal found 9/9$261
This Kiwi.com deal was found by Cheapflights users on 9/11. 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.
Thu 10/3010:57 amSTL - YYZ
1 stop26h 43mMultiple Airlines
Sun 11/24:00 pmYYZ - STL
2 stops42h 07mMultiple Airlines
Deal found 9/11$286
This Kiwi.com deal was found by Cheapflights users on 9/9. 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.
Thu 10/1610:57 amSTL - YYZ
1 stop11h 55mMultiple Airlines
Sun 10/194:00 pmYYZ - STL
2 stops27h 36mMultiple Airlines
Deal found 9/9$309
This Kiwi.com deal was found by Cheapflights users on 9/11. 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.
Thu 10/2310:57 amSTL - YYZ
1 stop26h 08mMultiple Airlines
Sun 10/268:00 pmYYZ - STL
2 stops24h 26mMultiple Airlines
Deal found 9/11$312
This American Airlines deal was found by Cheapflights users on 9/9. 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 10/176:00 amSTL - YYZ
1 stop10h 40mAmerican Airlines
Tue 10/2111:44 amYYZ - STL
1 stop9h 42mAmerican Airlines
Deal found 9/9$330
This Kiwi.com deal was found by Cheapflights users on 9/11. 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.
Thu 10/910:57 amSTL - YYZ
1 stop11h 55mMultiple Airlines
Mon 10/134:00 pmYYZ - STL
2 stops42h 07mMultiple Airlines
Deal found 9/11$331
This Kiwi.com deal was found by Cheapflights users on 9/10. 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.
Wed 9/247:55 pmSTL - YYZ
2 stops23h 03mMultiple Airlines
Sat 10/49:35 amYYZ - STL
1 stop25h 27mMultiple Airlines
Deal found 9/10$337
This American Airlines deal was found by Cheapflights users on 9/9. 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 10/176:00 amSTL - YYZ
1 stop10h 40mAmerican Airlines
Thu 10/306:30 amYYZ - STL
1 stop10h 34mAmerican Airlines
Deal found 9/9$346
This Kiwi.com deal was found by Cheapflights users on 9/9. 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.
Fri 10/39:32 pmSTL - YYZ
1 stop15h 20mMultiple Airlines
Mon 10/64:00 pmYYZ - STL
2 stops27h 36mMultiple Airlines
Deal found 9/9$348
This Kiwi.com deal was found by Cheapflights users on 9/10. 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.
Thu 10/2310:57 amSTL - YYZ
1 stop8h 58mMultiple Airlines
Sat 10/252:50 pmYYZ - STL
2 stops19h 32mMultiple Airlines
Deal found 9/10$349
This Kiwi.com deal was found by Cheapflights users on 9/9. 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.
Fri 10/246:42 pmSTL - YOW
1 stop21h 15mMultiple Airlines
Fri 10/315:40 amYOW - STL
2 stops15h 32mMultiple Airlines
Deal found 9/9$355
This American Airlines deal was found by Cheapflights users on 9/10. 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 10/254:34 pmSTL - YUL
1 stop18h 06mAmerican Airlines
Sat 11/112:30 pmYUL - STL
1 stop10h 38mAmerican Airlines
Deal found 9/10$377

Cheapflights Fare Finder

 
Customize your flight search to find flights from St. Louis to Ontario 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 September 11, 2025.
Use the filters below to find and compare flights from St. Louis to Ontario that are best for you.

Fly from

St. Louis

Fly to

Ontario

Route

Depart

Return

Price

St. LouisOttawa

STL - YOW

STLYOW

Lambert-St Louis

Fri 10/24

6:42 pm-4:57 pm

1 stop21h 15m

Ottawa

Fri 10/31

5:40 am-8:12 pm

2 stops15h 32m

$355

St. LouisMontreal

STL - YUL

STLYUL

Lambert-St Louis

Sat 10/25

4:34 pm-11:40 am

1 stop18h 06m

Montreal Pierre Elliott Trudeau Intl

Sat 11/1

12:30 pm-10:08 pm

1 stop10h 38m

$377

St. LouisToronto

STL - YYZ

STLYYZ

Lambert-St Louis

Thu 10/23

10:57 am-11:52 pm

1 stop11h 55m

Toronto Pearson Intl

Sat 10/25

12:00 pm-10:02 am

3 stops23h 02m

$379

St. LouisToronto

STL - YYZ

STLYYZ

Lambert-St Louis

Thu 10/9

10:57 am-11:52 pm

1 stop11h 55m

Toronto Pearson Intl

Sat 10/11

6:30 am-6:10 pm

1 stop12h 40m

$409

St. LouisMontreal

STL - YUL

STLYUL

Lambert-St Louis

Fri 12/5

9:45 am-10:10 pm

2 stops11h 25m

Montreal Pierre Elliott Trudeau Intl

Mon 12/8

4:35 pm-10:46 pm

1 stop31h 11m

$409

St. LouisToronto

STL - YYZ

STLYYZ

Lambert-St Louis

Fri 10/17

5:30 am-11:10 am

1 stop4h 40m

Toronto Pearson Intl

Thu 10/30

1:15 pm-11:54 pm

1 stop11h 39m

$428

St. LouisMontreal

STL - YUL

STLYUL

Lambert-St Louis

Fri 10/17

8:05 pm-11:40 am

1 stop14h 35m

Montreal Pierre Elliott Trudeau Intl

Mon 10/20

5:24 pm-8:09 am

1 stop15h 45m

$428

St. LouisMontreal

STL - YUL

STLYUL

Lambert-St Louis

Fri 10/3

9:32 pm-2:20 pm

1 stop15h 48m

Montreal Pierre Elliott Trudeau Intl

Sat 10/11

7:20 pm-10:37 am

2 stops16h 17m

$429

St. LouisToronto

STL - YYZ

STLYYZ

Lambert-St Louis

Thu 10/9

10:57 am-10:40 pm

2 stops10h 43m

Toronto Pearson Intl

Thu 10/16

6:30 am-12:00 pm

3 stops30h 30m

$442

St. LouisMontreal

STL - YUL

STLYUL

Lambert-St Louis

Thu 11/6

7:58 pm-3:11 pm

1 stop18h 13m

Montreal Pierre Elliott Trudeau Intl

Sun 11/9

3:52 pm-8:09 am

1 stop17h 17m

$444

Flights are sorted by cheapest round-trip flights first.

Deals found on 9/9

Showing 1-10 of 42 results
1
2
3
...
5

Best time to book a flight from St. Louis to Ontario

Have a flexible travel schedule? Discover the best time to fly to Ontario from St. Louis 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 St. Louis to Ontario

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

Currently, January is the cheapest month in which you can book a flight from St. Louis to Region of Ontario (average of $243). Flying from St. Louis to Region of Ontario in August is currently the most expensive (average of $348). 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 STL to ON?

Find hourly flight availability from St. Louis to Ontario. Discover flight options and departure times throughout the day, allowing you to choose a departure time that suits your schedule. Data last updated September 11, 2025.

When flying from St. Louis to Region of Ontario, the time of day you decide to fly out makes little to no difference towards the overall price you’ll pay on tickets.

Weekly flight availability from St. Louis to Region of Ontario

Explore weekly flight availability from St. Louis to Ontario. 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 September 11, 2025.

The most flights from STL to CAON are scheduled on a Monday (5 on average). You will have fewer flight options on Monday, which is when the least amount of flights are scheduled (5 on average).

Reviews of airlines servicing Ontario

Get insights into the airlines that provide service to Ontario. Read reviews, discover amenities, and learn about the overall travel experience offered by airlines. Use this information to make informed decisions when choosing an airline for your flight to Ontario. Reviews last updated September 11, 2025.
Get a feel of what it's like to fly with Delta, United Airlines, and American Airlines from St. Louis to Ontario by reading reviews from past customers. You can also see how each airline compares in terms of entertainment options, comfort, food, crew/service, and boarding process.
Delta
8.0
Very good
7,960 reviews

Boarding

8.2

Entertainment

7.9

Comfort

7.9

Food

7.3

Crew

8.5

Overall

8.0

Reviews

1 / 20
10.0
Excellent

Kim,May 2025

PIH - SLC

This trip was fine even with delay I had plenty of time to get connection flight!
Delta
8.0
Very good
7,960 reviews
Delta
8.0
Very good
7,960 reviews

Boarding

8.2

Entertainment

7.9

Comfort

7.9

Food

7.3

Crew

8.5

Overall

8.0

Reviews

1 / 20
10.0
Excellent

Kim,May 2025

PIH - SLC

This trip was fine even with delay I had plenty of time to get connection flight!
United Airlines
7.4
Good
8,937 reviews
Delta
8.0
Very good
7,960 reviews

Boarding

8.2

Entertainment

7.9

Comfort

7.9

Food

7.3

Crew

8.5

Overall

8.0

Reviews

1 / 20
10.0
Excellent

Kim,May 2025

PIH - SLC

This trip was fine even with delay I had plenty of time to get connection flight!
American Airlines
7.2
Good
10,000 reviews
Delta
8.0
Very good
7,960 reviews

Boarding

8.2

Entertainment

7.9

Comfort

7.9

Food

7.3

Crew

8.5

Overall

8.0

Reviews

1 / 20
10.0
Excellent

Kim,May 2025

PIH - SLC

This trip was fine even with delay I had plenty of time to get connection flight!
Air Canada
7.1
Good
10,000 reviews
Delta
8.0
Very good
7,960 reviews

Boarding

8.2

Entertainment

7.9

Comfort

7.9

Food

7.3

Crew

8.5

Overall

8.0

Reviews

1 / 20
10.0
Excellent

Kim,May 2025

PIH - SLC

This trip was fine even with delay I had plenty of time to get connection flight!

Related info for your journey

Find useful and relevant information for your journey from St. Louis to Ontario. 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 from for flights from St. Louis to Ontario?

    Lambert-St Louis (STL) is the airport you will fly out of if you book a flight from St. Louis to Ontario. It is only a 12.7 mi journey to Lambert-St Louis (STL) from St. Louis’s city center.

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

    Departing from St. Louis to Region of Ontario will take you 9h 52m. Airlines will cover a distance of 878 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 St. Louis to Region of Ontario?

    When deciding which route to take from St. Louis to Region of Ontario consider Lambert-St Louis - Toronto Pearson Intl, Lambert-St Louis - Montreal Pierre Elliott Trudeau Intl or Lambert-St Louis - Ottawa as they are the most popular.

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

    No one likes to see their flight delayed. When booking a flight from St. Louis to Region of Ontario consider choosing Air Canada (86%), Jazz (86%) or United Airlines (57%) as they are the most reliable in getting you off to your destination on time.

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

    Looking for the cheapest flight from St. Louis to Region of Ontario? While on average our users pay $1,023, our data indicates the cheapest price to be $252. The most popular route (Lambert-St Louis - Toronto Pearson Intl), is priced around $261.

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

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

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

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

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

    Yes. Cheapflights offers flight deals from St. Louis to Ontario 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 St. Louis to Region of Ontario?

    Currently, January is the cheapest month in which you can book a flight from St. Louis to Region of Ontario (average of $243). Flying from St. Louis to Region of Ontario in August is currently the most expensive (average of $348). 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

Browse thousands of different options on Cheapflights for your next trip

Toggle through the tabs below to find thousands of options on Cheapflights for your next trip.

Alternative routes for St. Louis to Ontario

See prices for flight routes from nearby airports that may be better suited for you.
St. Louis to Pearson Intl flights
St. Louis to Vancouver Intl flights
St. Louis to Pierre Elliott Trudeau Intl flights
Kansas City to Vancouver Intl flights
St. Louis to Calgary flights
Kansas City to Pierre Elliott Trudeau Intl flights
Kansas City to Pearson Intl flights
Kansas City to Calgary flights
St. Louis to Québec City flights
St. Louis to Halifax flights
Kansas City to Québec City flights
Kansas City to Kelowna flights
Springfield to Calgary flights
St. Louis to Edmonton flights
Kansas City to Edmonton flights
Kansas City to Halifax flights
Kansas City to Winnipeg flights
Columbia to Pearson Intl flights
Springfield to Pierre Elliott Trudeau Intl flights
St. Louis to Sydney flights
St. Louis to Winnipeg flights
St. Louis to Victoria flights
Kansas City to Victoria flights
St. Louis to Kelowna flights
Kansas City to Toronto Island flights
Kansas City to Ottawa flights
Springfield to Vancouver Intl flights
Springfield to Pearson Intl flights
St. Louis to Ottawa flights
St. Louis to Saskatoon flights
St. Louis to St. John's flights
Kansas City to St. John's flights
Joplin to Pearson Intl flights
Columbia to Pierre Elliott Trudeau Intl flights
St. Louis to Grande Prairie flights
Kansas City to Saskatoon flights
Joplin to Pierre Elliott Trudeau Intl flights
Springfield to Toronto Island flights
Kansas City to Moncton flights

Top 3 airlines flying from St. Louis to Ontario

Discover the top 3 airlines that operate flights from St. Louis to Ontario. 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 September 11, 2025.
AirlineCheapestAverageFlexibilityOn-time
United AirlinesCheapest$214Average$667FlexibilityNo cancel feeOn-time69%
Air CanadaCheapest$220Average$657FlexibilityNo cancel feeOn-time67%
American AirlinesCheapest$330Average$612FlexibilityNo cancel feeOn-time71%

100% Free

Cheapflights is completely free to use, so you can start saving the moment you arrive.

Book with Flexibility

Our users can plan ahead with confidence and find flights with no change fees

Travel Smart

Millions of people come to us for their flight needs every year. We help make travel planning easy by providing useful insights and data-driven graphs that can inform your decisions.