HomeSearch by dateVacation packagesHotelsFlight dealsCar rentalTravel tips & news
Ontario

$154+ 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 4/2. Fares are subject to change and may not be available on all flights or dates of travel.
STL — YYZ
Apr 18 — Apr 251
Sat 4/18
Sat 4/25
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

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 March 19, 2026.

This Air Canada 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 Air Canada is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 6/67:05 am
STL
-
YOW
1 stop5h 00m
Air Canada
Sat 6/137:00 am
YOW
-
STL
1 stop6h 06m
Air Canada
Deal found 3/19$346
This American Airlines deal was found by Cheapflights users on 3/17. 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 4/144:30 pm
STL
-
YUL
1 stop18h 14m
American Airlines
Tue 4/2112:30 pm
YUL
-
STL
1 stop10h 49m
American Airlines
Deal found 3/17$347
This flugladen.de deal was found by Cheapflights users on 3/17. 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 flugladen.de is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 5/11:00 pm
STL
-
YOW
1 stop6h 51m
Air Canada
Fri 5/83:00 pm
YOW
-
STL
1 stop6h 25m
Air Canada
Deal found 3/17$355
This Kissandfly.com 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 Kissandfly.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 4/287:45 am
STL
-
YOW
1 stop5h 14m
Lufthansa
Tue 5/510:44 am
YOW
-
STL
1 stop6h 55m
Lufthansa
Deal found 3/14$365
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.
Wed 4/159:10 am
STL
-
YOW
1 stop6h 57m
United Airlines
Sun 4/196:00 am
YOW
-
STL
1 stop5h 28m
United Airlines
Deal found 3/15$366
This United Airlines deal was found by Cheapflights users on 3/17. 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 4/146:30 am
STL
-
YOW
2 stops6h 52m
United Airlines
Thu 4/165:25 pm
YOW
-
STL
1 stop4h 48m
United Airlines
Deal found 3/17$375
This United 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 United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 6/51:13 pm
STL
-
YOW
2 stops9h 41m
United Airlines
Sun 6/76:00 am
YOW
-
STL
2 stops10h 46m
United Airlines
Deal found 3/14$381
This Billigflug 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 Billigflug is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 4/287:45 am
STL
-
YOW
2 stops10h 10m
Air Canada
Tue 5/56:25 am
YOW
-
STL
1 stop15h 48m
Air Canada
Deal found 3/14$382
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 4/138:41 am
STL
-
YYZ
1 stop14h 33m
Multiple Airlines
Sun 4/196:30 am
YYZ
-
STL
2 stops25h 20m
Multiple Airlines
Deal found 3/16$383
This American Airlines deal was found by Cheapflights users on 3/17. 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 4/298:03 pm
STL
-
YUL
1 stop14h 41m
American Airlines
Mon 5/412:30 pm
YUL
-
STL
1 stop12h 16m
American Airlines
Deal found 3/17$383
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 4/134:59 pm
STL
-
YYZ
1 stop20h 17m
Multiple Airlines
Mon 4/209:35 am
YYZ
-
STL
2 stops46h 15m
Multiple Airlines
Deal found 3/16$388
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.
Wed 5/131:05 pm
STL
-
YOW
1 stop6h 46m
Air Canada
Sun 5/172:35 pm
YOW
-
STL
1 stop6h 50m
Air Canada
Deal found 3/18$392

Find 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 March 19, 2026.

Most accurate provider

FlightHub
3 stars

Most trusted provider

FlightHub
3 stars

Round-trip from

$346
(Air Canada)

One-way from

$154
(United Airlines)

Popular in

November

Cheapest in

June

Average price

$427

Good round-trip deal

$724 or less

Good one-way deal

$347 or less
Provider with most accurate pricing for Lambert-St Louis-Toronto (YTO) flight deals.
Search Deals
Provider most trusted by Cheapflights users for Lambert-St Louis-Toronto (YTO) flights.
Search Deals
From Lambert-St Louis to Ontario
Search Deals
One-way flight from Lambert-St Louis to Ontario
Search Deals
Highest demand for flights based on searches. 10% potential increase in price ($59 potential increase over avg. RT price).
Search Deals
Cheapest flight prices on average. 3% potential price decrease ($16 potential savings vs. average RT price).
Search Deals
Average for round-trip flights in March 2026
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

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 March 19, 2026.
Use the filters below to find and compare flights from St. Louis to Ontario that are best for you.

Fly from

Fly to

Route

Depart

Return

Price

Cheapest round-trip

St. LouisOttawa

STL - YOW

STLYOW

Lambert-St Louis

Tue 4/28

7:45 am-1:59 pm

1 stop5h 14m

Ottawa

Tue 5/5

10:44 am-4:39 pm

1 stop6h 55m

$365

St. LouisOttawa

STL - YOW

STLYOW

Lambert-St Louis

Wed 4/15

9:10 am-5:07 pm

1 stop6h 57m

Ottawa

Sun 4/19

6:00 am-10:28 am

1 stop5h 28m

$366

St. LouisOttawa

STL - YOW

STLYOW

Lambert-St Louis

Wed 7/15

1:13 pm-9:35 pm

1 stop7h 22m

Ottawa

Sun 7/26

6:25 am-12:11 pm

1 stop6h 46m

$366

St. LouisOttawa

STL - YOW

STLYOW

Lambert-St Louis

Tue 4/14

9:10 am-5:07 pm

1 stop6h 57m

Ottawa

Thu 4/16

6:25 am-10:45 am

1 stop5h 20m

$366

St. LouisOttawa

STL - YOW

STLYOW

Lambert-St Louis

Thu 4/30

7:45 am-9:35 pm

1 stop12h 50m

Ottawa

Thu 5/7

6:00 am-9:13 pm

2 stops16h 13m

$376

St. LouisOttawa

STL - YOW

STLYOW

Lambert-St Louis

Sat 6/6

6:00 am-6:48 pm

2 stops11h 48m

Ottawa

Sat 6/13

6:25 am-10:34 am

1 stop5h 09m

$376

St. LouisMontreal

STL - YUL

STLYUL

Lambert-St Louis

Tue 4/21

9:10 am-6:56 pm

1 stop8h 46m

Montreal Pierre Elliott Trudeau Intl

Sat 4/25

9:15 am-9:13 pm

1 stop12h 58m

$508

St. LouisMontreal

STL - YUL

STLYUL

Lambert-St Louis

Sat 5/2

7:05 am-9:37 pm

2 stops13h 32m

Montreal Pierre Elliott Trudeau Intl

Sat 5/9

1:03 pm-11:56 pm

2 stops11h 53m

$531

St. LouisToronto

STL - YYZ

STLYYZ

Lambert-St Louis

Wed 7/22

6:00 am-12:16 pm

1 stop5h 16m

Toronto Pearson Intl

Sun 7/26

6:15 am-12:54 pm

1 stop7h 39m

$541

St. LouisToronto

STL - YYZ

STLYYZ

Lambert-St Louis

Mon 4/13

7:45 am-1:42 pm

1 stop4h 57m

Toronto Pearson Intl

Wed 4/15

1:00 pm-7:31 pm

1 stop7h 31m

$549

Flights are sorted by cheapest round-trip flights first.

Deals found on 3/15

Showing 1-10 of 48 resultsSorted by cheapest first
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, June is the cheapest month in which you can book a flight from St. Louis to Region of Ontario (average of $177). Flying from St. Louis to Region of Ontario in January is currently the most expensive (average of $781). 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 March 19, 2026.

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 March 19, 2026.

The most flights from STL to CAON 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).

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 March 19, 2026.
Get a feel of what it's like to fly with Delta,United Airlines, andAmerican 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
7.9
Good
8,296 reviews

Overall

7.9

Crew

8.5

Boarding

8.1

Food

7.2

Entertainment

7.8

Comfort

7.9

Reviews

1 / 20
6.0
Good

Jim,Nov 2025

AVL - ATL

The exit row seats without a seat in front are great for leg room but don’t have a fold out entertainment console so you’re forced to use the screen several feet in front of you (there is, at least, a remote). Best to bring a tablet loaded with entertainment or a book.
Delta
7.9
Good
8,296 reviews
Delta
7.9
Good
8,296 reviews

Overall

7.9

Crew

8.5

Boarding

8.1

Food

7.2

Entertainment

7.8

Comfort

7.9

Reviews

1 / 20
6.0
Good

Jim,Nov 2025

AVL - ATL

The exit row seats without a seat in front are great for leg room but don’t have a fold out entertainment console so you’re forced to use the screen several feet in front of you (there is, at least, a remote). Best to bring a tablet loaded with entertainment or a book.
United Airlines
7.4
Good
9,441 reviews
Delta
7.9
Good
8,296 reviews

Overall

7.9

Crew

8.5

Boarding

8.1

Food

7.2

Entertainment

7.8

Comfort

7.9

Reviews

1 / 20
6.0
Good

Jim,Nov 2025

AVL - ATL

The exit row seats without a seat in front are great for leg room but don’t have a fold out entertainment console so you’re forced to use the screen several feet in front of you (there is, at least, a remote). Best to bring a tablet loaded with entertainment or a book.
American Airlines
7.1
Good
11,475 reviews
Delta
7.9
Good
8,296 reviews

Overall

7.9

Crew

8.5

Boarding

8.1

Food

7.2

Entertainment

7.8

Comfort

7.9

Reviews

1 / 20
6.0
Good

Jim,Nov 2025

AVL - ATL

The exit row seats without a seat in front are great for leg room but don’t have a fold out entertainment console so you’re forced to use the screen several feet in front of you (there is, at least, a remote). Best to bring a tablet loaded with entertainment or a book.
Air Canada
7.1
Good
10,815 reviews
Delta
7.9
Good
8,296 reviews

Overall

7.9

Crew

8.5

Boarding

8.1

Food

7.2

Entertainment

7.8

Comfort

7.9

Reviews

1 / 20
6.0
Good

Jim,Nov 2025

AVL - ATL

The exit row seats without a seat in front are great for leg room but don’t have a fold out entertainment console so you’re forced to use the screen several feet in front of you (there is, at least, a remote). Best to bring a tablet loaded with entertainment or a book.

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 5h 14m. 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 cheapest airlines to fly from St. Louis to Region of Ontario one-way?

    One-way options have recently been found by users for as low as $142 on United Airlines. Other airlines that offer cheap prices include Air Canada from $177 and Delta from $186 one-way.

  • 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 United Airlines (72%), Air Canada (71%) or Jazz (71%) 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 $1,098, our data indicates the cheapest price to be $266. The most popular route (Lambert-St Louis - Toronto Pearson Intl), is priced around $440.

  • 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, June is the cheapest month in which you can book a flight from St. Louis to Region of Ontario (average of $177). Flying from St. Louis to Region of Ontario in January is currently the most expensive (average of $781). 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.

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 March 19, 2026.
AirlineCheapestAverageFlexibilityOn-time
Air CanadaCheapest$139Average$623FlexibilityNo cancel feeOn-time67%
United AirlinesCheapest$199Average$601FlexibilityNo cancel feeOn-time69%
American AirlinesCheapest$270Average$558FlexibilityNo 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.
Site
©2026 Cheapflights