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$137+ 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 9/27. Fares are subject to change and may not be available on all flights or dates of travel.
STL — YYZ
ago. 4 — ago. 111
lun. 8/4
lun. 8/11
1 adult, Economy
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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 julio 30, 2025.

Round-trip from

$331
(American Airlines)

One-way from

$145
(American Airlines)

Popular in

March

Cheapest in

January

Average price

$489

Good round-trip deal

$667 or less

Good one-way deal

$387 or less
From Lambert-St Louis to Ontario
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One-way flight from Lambert-St Louis to Ontario
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High demand for flights, 2% potential price rise
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Cheapest flight prices on average. 3% potential price decrease ($14 potential savings vs. average RT price).
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Average for round-trip flights in July 2025
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Price to beat on a round-trip flight from Lambert-St Louis to Ontario.
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Price to beat on a one-way flight from Lambert-St Louis to Ontario.
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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 julio 30, 2025.

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.
mar. 8/266:06 amSTL - YYZ
1 stop10h 35mAmerican Airlines
mar. 9/23:14 pmYYZ - STL
1 stop8h 03mAmerican Airlines
Deal found 7/27$331
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.
mié. 9/106:10 amSTL - YUL
1 stop9h 23mAmerican Airlines
lun. 9/155:15 pmYUL - STL
1 stop17h 11mAmerican Airlines
Deal found 7/30$348
This Mytrip 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 Mytrip is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
jue. 9/412:05 pmSTL - YYZ
2 stops22h 30mMultiple Airlines
sáb. 9/67:00 amYYZ - STL
3 stops28h 50mMultiple Airlines
Deal found 7/29$355
This Air Canada 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 Air Canada is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
jue. 9/44:05 pmSTL - YYZ
Nonstop1h 55mAir Canada
dom. 9/76:35 pmYYZ - STL
Nonstop2h 03mAir Canada
Deal found 7/29$437
This United 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 United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
mar. 8/269:17 amSTL - YYZ
2 stops11h 57mUnited Airlines
mar. 9/28:15 amYYZ - STL
1 stop8h 29mUnited Airlines
Deal found 7/27$441
This Mytrip 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 Mytrip is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
jue. 11/612:20 pmSTL - YUL
1 stop11h 25mMultiple Airlines
dom. 11/98:00 amYUL - STL
3 stops29h 00mMultiple Airlines
Deal found 7/28$456
This Delta 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 Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
mié. 9/39:16 amSTL - YYZ
1 stop10h 27mDelta
jue. 9/116:44 pmYYZ - STL
1 stop14h 12mDelta
Deal found 7/30$466
This Air Canada 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 Air Canada is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
mié. 9/101:30 pmSTL - YUL
Nonstop2h 30mAir Canada
mié. 9/179:15 amYUL - STL
1 stop7h 03mAir Canada
Deal found 7/29$520
This United 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 United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
mar. 9/27:04 pmSTL - YUL
2 stops20h 56mUnited Airlines
sáb. 9/66:15 amYUL - STL
1 stop10h 29mUnited Airlines
Deal found 7/28$526
This Delta 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 Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
mié. 9/1010:45 amSTL - YUL
2 stops10h 02mDelta
mié. 9/1711:00 amYUL - STL
1 stop10h 05mDelta
Deal found 7/29$527
This Kiwi.com 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 Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
jue. 8/1410:37 amSTL - YOW
1 stop29h 43mMultiple Airlines
mar. 8/195:55 amYOW - STL
2 stops18h 29mMultiple Airlines
Deal found 7/27$612
This United 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 United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
sáb. 9/139:17 amSTL - YOW
1 stop11h 18mUnited Airlines
sáb. 9/2010:37 amYOW - STL
1 stop9h 50mUnited Airlines
Deal found 7/30$621

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 julio 30, 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. LouisToronto

STL - YYZ

STLYYZ

Lambert-St Louis

mar. 8/26

6:06 am-5:41 pm

1 stop10h 35m

Toronto Pearson Intl

mar. 9/2

3:14 pm-10:17 pm

1 stop8h 03m

$331

St. LouisMontreal

STL - YUL

STLYUL

Lambert-St Louis

mié. 9/10

6:10 am-4:33 pm

1 stop9h 23m

Montreal Pierre Elliott Trudeau Intl

lun. 9/15

5:15 pm-9:26 am

1 stop17h 11m

$348

St. LouisToronto

STL - YYZ

STLYYZ

Lambert-St Louis

jue. 9/4

12:05 pm-11:35 am

2 stops22h 30m

Toronto Pearson Intl

sáb. 9/6

7:00 am-10:50 am

3 stops28h 50m

$355

St. LouisToronto

STL - YYZ

STLYYZ

Lambert-St Louis

jue. 9/4

4:05 pm-7:00 pm

Nonstop1h 55m

Toronto Pearson Intl

dom. 9/7

6:35 pm-7:38 pm

Nonstop2h 03m

$437

St. LouisToronto

STL - YYZ

STLYYZ

Lambert-St Louis

mar. 8/26

9:17 am-10:14 pm

2 stops11h 57m

Toronto Pearson Intl

mar. 9/2

8:15 am-3:44 pm

1 stop8h 29m

$441

St. LouisToronto

STL - YYZ

STLYYZ

Lambert-St Louis

mié. 9/3

9:16 am-8:43 pm

1 stop10h 27m

Toronto Pearson Intl

jue. 9/11

6:44 pm-7:56 am

1 stop14h 12m

$466

St. LouisMontreal

STL - YUL

STLYUL

Lambert-St Louis

dom. 9/21

10:35 am-12:27 am

2 stops12h 52m

Montreal Pierre Elliott Trudeau Intl

dom. 9/28

6:00 am-10:50 am

1 stop5h 50m

$500

St. LouisMontreal

STL - YUL

STLYUL

Lambert-St Louis

mié. 9/10

1:30 pm-5:00 pm

Nonstop2h 30m

Montreal Pierre Elliott Trudeau Intl

mié. 9/17

9:15 am-3:18 pm

1 stop7h 03m

$520

St. LouisMontreal

STL - YUL

STLYUL

Lambert-St Louis

mar. 9/2

7:04 pm-5:00 pm

2 stops20h 56m

Montreal Pierre Elliott Trudeau Intl

sáb. 9/6

6:15 am-3:44 pm

1 stop10h 29m

$526

St. LouisMontreal

STL - YUL

STLYUL

Lambert-St Louis

mié. 9/10

10:45 am-9:47 pm

2 stops10h 02m

Montreal Pierre Elliott Trudeau Intl

mié. 9/17

11:00 am-8:05 pm

1 stop10h 05m

$527

Flights are sorted by cheapest round-trip flights first.

Deals found on 7/28

Showing 1-10 of 25 results
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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 julio 30, 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 julio 30, 2025.

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

How much does it cost to fly round-trip from St. Louis to Region of Ontario?

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 julio 30, 2025.
Get a feel of what it's like to fly with Alaska Airlines, Delta, and United 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.
Alaska Airlines
8.0
Very good
10,000 reviews

Food

7.1

Comfort

7.8

Entertainment

7.1

Boarding

8.1

Crew

8.5

Overall

8.0

Reviews

1 / 20
10.0
Excellent

Jonathan,Jul 2025

SEA - BOS

Fantastic Check-in with easy baggage drop. While it took a while to find out which was the gate, the boarding was a dream, the stewards were simply incredible and the flight fantastic.
Alaska Airlines
8.0
Very good
10,000 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Food

7.1

Comfort

7.8

Entertainment

7.1

Boarding

8.1

Crew

8.5

Overall

8.0

Reviews

1 / 20
10.0
Excellent

Jonathan,Jul 2025

SEA - BOS

Fantastic Check-in with easy baggage drop. While it took a while to find out which was the gate, the boarding was a dream, the stewards were simply incredible and the flight fantastic.
Delta
8.0
Very good
7,980 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Food

7.1

Comfort

7.8

Entertainment

7.1

Boarding

8.1

Crew

8.5

Overall

8.0

Reviews

1 / 20
10.0
Excellent

Jonathan,Jul 2025

SEA - BOS

Fantastic Check-in with easy baggage drop. While it took a while to find out which was the gate, the boarding was a dream, the stewards were simply incredible and the flight fantastic.
United Airlines
7.4
Good
8,896 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Food

7.1

Comfort

7.8

Entertainment

7.1

Boarding

8.1

Crew

8.5

Overall

8.0

Reviews

1 / 20
10.0
Excellent

Jonathan,Jul 2025

SEA - BOS

Fantastic Check-in with easy baggage drop. While it took a while to find out which was the gate, the boarding was a dream, the stewards were simply incredible and the flight fantastic.
American Airlines
7.2
Good
10,000 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Food

7.1

Comfort

7.8

Entertainment

7.1

Boarding

8.1

Crew

8.5

Overall

8.0

Reviews

1 / 20
10.0
Excellent

Jonathan,Jul 2025

SEA - BOS

Fantastic Check-in with easy baggage drop. While it took a while to find out which was the gate, the boarding was a dream, the stewards were simply incredible and the flight fantastic.
Air Canada
7.1
Good
9,837 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Food

7.1

Comfort

7.8

Entertainment

7.1

Boarding

8.1

Crew

8.5

Overall

8.0

Reviews

1 / 20
10.0
Excellent

Jonathan,Jul 2025

SEA - BOS

Fantastic Check-in with easy baggage drop. While it took a while to find out which was the gate, the boarding was a dream, the stewards were simply incredible and the flight fantastic.

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.

  • 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 $145 on American Airlines. Other airlines that offer cheap prices include Delta from $187 and United Airlines from $225 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 (80%), Air Canada (78%) or Jazz (75%) 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 $1,845, our data indicates the cheapest price to be $237. The most popular route (Lambert-St Louis - Toronto Pearson Intl), is priced around $355.

  • 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.

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Alternative routes for St. Louis to Ontario

See prices for flight routes from nearby airports that may be better suited for you.
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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 julio 30, 2025.
AirlineCheapestAverageFlexibilityOn-time
United AirlinesCheapest$214Average$656FlexibilityNo cancel feeOn-time69%
Air CanadaCheapest$220Average$645FlexibilityNo cancel feeOn-time67%
American AirlinesCheapest$330Average$590FlexibilityNo cancel feeOn-time71%

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