What are the cheapest airlines to fly from St. Louis to Region of Ontario one-way?

For one-way options, check prices for American Airlines. According to our data, you can fly for as low as C$ 269. Users have also found prices from C$ 272 and C$ 275 on Delta and Air Canada, respectively.

What are the most popular routes from St. Louis to Region of Ontario?

The most popular flight routes from St. Louis to Region of Ontario are Lambert-St Louis - Montreal Pierre Elliott Trudeau Intl, Lambert-St Louis - Toronto Pearson Intl and Lambert-St Louis - London.

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

The cheapest flight price from St. Louis to Region of Ontario is C$ 192. On average you can expect to pay C$ 236. The most popular route, (Lambert-St Louis - Montreal Pierre Elliott Trudeau Intl), can usually be booked for C$ 581.

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

Before booking your flight to Region of Ontario from St. Louis, check out the most reliable airlines to get you to your destination on time: Air Canada (78%), Jazz (78%), United Airlines( 78%).

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

When searching for a good deal, it’s best to be prepared for potential fluctuations in price. We recommend booking at least 53 days in advance, which can save you up to 399% on flights from St. Louis to Region of Ontario compared to booking the week you need them. Waiting 53 days out may not be for everyone, so we have options available for flights within the next two weeks, with the lowest price starting at C$ 435. For sooner than that we have options available in the next 3 days from C$ 1,260.

What is the cheapest month to fly from St. Louis to Region of Ontario?

May is one of the best times of the year to fly to Region of Ontario from St. Louis. Prices for May average C$ 557 per person but you can even find prices for as low as C$ 309. The most expensive prices can be found in the month of March. Opting for a May flight can save you 45% on your journey compared to booking in March

What airport do you fly from for flights from St. Louis to Ontario?

If you book a flight to Ontario from St. Louis, you will be flying from Lambert-St Louis, which is the city’s only airport. Lambert-St Louis (STL) is located 20.4 km from the centre of St. Louis.

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.

C$ 171+ Flights from St. Louis to Ontario

Cheap flight deals from St. Louis to Ontario

Round-trip from	C$ 440
One-way from	C$ 171
Popular in	March
Cheapest in	May
Average price	C$ 435
Good one-way deal	C$ 231 or less

5/6-9/6
2 total stops
18h 27m total
St. Louis to Ontario

Search Deals

9/5
2 total stops
24h 01m total
St. Louis to Ontario

Search Deals

Highest demand for flights based on searches. 3% potential increase in price (C$ 24 potential increase over avg. RT price).

Search Deals

Cheapest flight prices on average. 4% potential price decrease (C$ 32 potential savings vs. average RT price).

Search Deals

Average for round-trip flights in April 2025

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 17 April 2025.

Thu 5/610:10 a.m.STL - YYZ

1 stop9h 50mMultiple Airlines

Mon 9/64:00 p.m.YYZ - STL

1 stop8h 37mMultiple Airlines

Deal found 17/4C$ 440

Thu 15/510:10 a.m.STL - YUL

2 stops13h 27mMultiple Airlines

Thu 22/56:45 a.m.YUL - STL

1 stop18h 07mMultiple Airlines

Deal found 17/4C$ 573

Thu 15/57:30 a.m.STL - YYZ

Nonstop1h 55mAir Canada

Sun 18/53:00 p.m.YYZ - STL

1 stop5h 58mAir Canada

Deal found 15/4C$ 593

Tue 3/67:32 a.m.STL - YYZ

1 stop10h 03mAmerican Airlines

Tue 10/611:40 a.m.YYZ - STL

1 stop9h 50mAmerican Airlines

Deal found 17/4C$ 603

Mon 5/55:34 p.m.STL - YYZ

1 stop4h 41mDelta

Tue 20/57:55 a.m.YYZ - STL

1 stop13h 53mDelta

Deal found 17/4C$ 624

Fri 2/51:30 p.m.STL - YUL

Nonstop2h 30mAir Canada

Sun 4/56:10 p.m.YUL - STL

Nonstop2h 48mAir Canada

Deal found 16/4C$ 642

Tue 22/76:33 a.m.STL - YYZ

2 stops6h 46mUnited Airlines

Sat 26/72:10 p.m.YYZ - STL

Nonstop2h 06mUnited Airlines

Deal found 17/4C$ 649

Tue 27/56:00 a.m.STL - YUL

1 stop9h 04mDelta

Wed 28/55:00 p.m.YUL - STL

1 stop16h 07mDelta

Deal found 16/4C$ 652

Wed 11/66:04 a.m.STL - YUL

1 stop9h 41mAmerican Airlines

Tue 17/612:30 p.m.YUL - STL

1 stop9h 00mAmerican Airlines

Deal found 16/4C$ 678

Wed 28/58:15 a.m.STL - YUL

1 stop6h 34mUnited Airlines

Wed 28/56:10 p.m.YUL - STL

Nonstop2h 48mUnited Airlines

Deal found 16/4C$ 704

Fri 6/66:00 a.m.STL - YYZ

2 stops23h 52mWestJet

Sun 8/66:30 a.m.YYZ - STL

1 stop5h 02mWestJet

Deal found 16/4C$ 707

Sat 24/55:17 p.m.STL - YUL

1 stop4h 59mWestJet

Sat 31/56:00 a.m.YUL - STL

1 stop4h 35mWestJet

Deal found 16/4C$ 840

Best flights from St. Louis to Ontario
Discover carefully curated flight deals from St. Louis to Ontario that have cost, travel time, and layovers in mind to ensure you get the best travel experience. Data last updated 17 April 2025.

Thu 5/610:10 a.m.STL - YYZ

1 stop9h 50mMultiple Airlines

Mon 9/64:00 p.m.YYZ - STL

1 stop8h 37mMultiple Airlines

Deal found 17/4C$ 440

Thu 15/57:30 a.m.STL - YYZ

Nonstop1h 55mAir Canada

Sun 18/53:00 p.m.YYZ - STL

1 stop5h 58mAir Canada

Deal found 15/4C$ 593

Tue 3/67:32 a.m.STL - YYZ

1 stop10h 03mAmerican Airlines

Tue 10/611:40 a.m.YYZ - STL

1 stop9h 50mAmerican Airlines

Deal found 17/4C$ 603

Mon 5/55:34 p.m.STL - YYZ

1 stop4h 41mDelta

Wed 21/57:55 a.m.YYZ - STL

1 stop13h 53mDelta

Deal found 17/4C$ 624

Tue 22/76:33 a.m.STL - YYZ

2 stops6h 46mUnited Airlines

Sat 26/72:10 p.m.YYZ - STL

Nonstop2h 06mUnited Airlines

Deal found 17/4C$ 649

Fri 6/66:00 a.m.STL - YYZ

2 stops23h 52mWestJet

Sun 8/66:30 a.m.YYZ - STL

1 stop5h 02mWestJet

Deal found 16/4C$ 707

Wed 7/53:08 p.m.STL - YYZ

1 stop22h 52mAlaska Airlines

Thu 22/54:45 p.m.YYZ - STL

1 stop32h 19mAlaska Airlines

Deal found 17/4C$ 894

Thu 15/510:10 a.m.STL - YUL

2 stops13h 27mMultiple Airlines

Thu 22/56:45 a.m.YUL - STL

1 stop18h 07mMultiple Airlines

Deal found 17/4C$ 573

Fri 2/51:30 p.m.STL - YUL

Nonstop2h 30mAir Canada

Sun 4/56:10 p.m.YUL - STL

Nonstop2h 48mAir Canada

Deal found 16/4C$ 642

Tue 27/56:00 a.m.STL - YUL

1 stop9h 04mDelta

Wed 28/55:00 p.m.YUL - STL

1 stop16h 07mDelta

Deal found 16/4C$ 652

Wed 11/66:04 a.m.STL - YUL

1 stop9h 41mAmerican Airlines

Tue 17/612:30 p.m.YUL - STL

1 stop9h 00mAmerican Airlines

Deal found 16/4C$ 678

Wed 28/58:15 a.m.STL - YUL

1 stop6h 34mUnited Airlines

Wed 28/56:10 p.m.YUL - STL

Nonstop2h 48mUnited Airlines

Deal found 16/4C$ 704

Direct flights from St. Louis to Ontario
Explore direct flight options from St. Louis to Ontario based on user searches, and compare prices and availability for your desired travel dates. Data last updated 17 April 2025.

Thu 15/57:30 a.m.STL - YYZ

Nonstop1h 55mAir Canada

Sun 18/511:30 a.m.YYZ - STL

Nonstop2h 06mAir Canada

Deal found 15/4C$ 606

Mon 5/52:30 p.m.STL - YYZ

Nonstop2h 00mMultiple Airlines

Wed 7/56:30 p.m.YYZ - STL

Nonstop2h 13mMultiple Airlines

Deal found 17/4C$ 623

Fri 2/51:30 p.m.STL - YUL

Nonstop2h 30mAir Canada

Sun 4/56:10 p.m.YUL - STL

Nonstop2h 48mAir Canada

Deal found 16/4C$ 642

Thu 18/91:30 p.m.STL - YUL

Nonstop2h 30mUnited Airlines

Tue 23/96:10 p.m.YUL - STL

Nonstop2h 47mUnited Airlines

Deal found 16/4C$ 736

Fri 1/84:00 p.m.STL - YYZ

Nonstop2h 00mUnited Airlines

Sun 3/86:30 p.m.YYZ - STL

Nonstop2h 10mUnited Airlines

Deal found 16/4C$ 742

Last-minute flights from St. Louis to Ontario
Discover last-minute flight deals from St. Louis to Ontario. Data last updated 17 April 2025 and is based on user searches.

Wed 23/46:08 a.m.STL - YYZ

1 stop9h 02mDelta

Wed 30/46:15 a.m.YYZ - STL

1 stop9h 31mDelta

Deal found 17/4C$ 699

Wed 23/44:50 p.m.STL - YYZ

2 stops27h 35mMultiple Airlines

Wed 30/47:30 a.m.YYZ - STL

2 stops34h 45mMultiple Airlines

Deal found 17/4C$ 753

Wed 23/46:30 a.m.STL - YYZ

1 stop4h 19mAir Canada

Wed 30/47:45 p.m.YYZ - STL

Nonstop2h 13mAir Canada

Deal found 17/4C$ 756

Thu 24/45:41 p.m.STL - YUL

1 stop19h 29mMultiple Airlines

Sun 27/49:15 a.m.YUL - STL

1 stop9h 00mMultiple Airlines

Deal found 16/4C$ 707

Thu 24/46:30 a.m.STL - YUL

2 stops10h 20mUnited Airlines

Sun 27/48:30 a.m.YUL - STL

2 stops8h 17mUnited Airlines

Deal found 16/4C$ 1,030

Fri 25/45:35 p.m.STL - YYZ

2 stops15h 29mUnited Airlines

Mon 28/45:30 p.m.YYZ - STL

1 stop6h 45mUnited Airlines

Deal found 17/4C$ 908

Fri 2/51:30 p.m.STL - YUL

Nonstop2h 30mAir Canada

Sun 4/56:10 p.m.YUL - STL

Nonstop2h 48mAir Canada

Deal found 16/4C$ 642

Mon 5/55:34 p.m.STL - YYZ

1 stop4h 41mDelta

Tue 20/57:55 a.m.YYZ - STL

1 stop13h 53mDelta

Deal found 17/4C$ 624

Mon 5/57:31 a.m.STL - YUL

1 stop8h 24mAmerican Airlines

Mon 12/512:30 p.m.YUL - STL

1 stop12h 21mAmerican Airlines

Deal found 17/4C$ 681

Tue 6/55:45 p.m.STL - YYZ

1 stop19h 14mMultiple Airlines

Sat 10/54:00 p.m.YYZ - STL

2 stops27h 41mMultiple Airlines

Deal found 17/4C$ 449

Thu 8/56:00 a.m.STL - YYZ

1 stop7h 30mAmerican Airlines

Mon 19/51:15 p.m.YYZ - STL

1 stop11h 36mAmerican Airlines

Deal found 17/4C$ 603

Thu 8/51:09 p.m.STL - YYZ

1 stop9h 46mWestJet

Sun 18/56:30 a.m.YYZ - STL

1 stop4h 05mWestJet

Deal found 17/4C$ 735

One-way flights from St. Louis to Ontario
Search for one-way flight options from St. Louis to Ontario. Find affordable one-way fares based on user searches. Data last updated 17 April 2025.

Fri 9/59:55 p.m.STL - YYZ

2 stops24h 01mMultiple Airlines

Deal found 16/4C$ 171

Thu 15/510:10 a.m.STL - YUL

2 stops13h 27mMultiple Airlines

Deal found 17/4C$ 219

Thu 4/97:23 a.m.STL - YUL

1 stop8h 17mAmerican Airlines

Deal found 16/4C$ 269

Tue 27/56:00 a.m.STL - YUL

1 stop9h 04mDelta

Deal found 17/4C$ 272

Sun 8/67:30 a.m.STL - YYZ

Nonstop1h 55mAir Canada

Deal found 17/4C$ 275

Wed 4/612:30 p.m.STL - YYZ

1 stop9h 24mDelta

Deal found 17/4C$ 284

Wed 4/68:10 a.m.STL - YYZ

2 stops9h 55mUnited Airlines

Deal found 17/4C$ 298

Thu 4/91:30 p.m.STL - YUL

Nonstop2h 30mAir Canada

Deal found 16/4C$ 331

Tue 27/55:00 a.m.STL - YUL

2 stops12h 25mUnited Airlines

Deal found 17/4C$ 336

Fri 25/47:19 a.m.STL - YYZ

1 stop10h 11mAmerican Airlines

Deal found 16/4C$ 409

Cheapflights Fare Finder

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

St. LouisToronto

STL - YYZ

STLYYZ

Lambert-St Louis

Thu 5/6

10:10 a.m.-9:00 p.m.

1 stop9h 50m

Toronto Pearson Intl

Mon 9/6

4:00 p.m.-11:37 p.m.

1 stop8h 37m

C$ 440

St. LouisMontreal

STL - YUL

STLYUL

Lambert-St Louis

Thu 15/5

10:10 a.m.-12:37 a.m.

2 stops13h 27m

Montreal Pierre Elliott Trudeau Intl

Thu 22/5

6:45 a.m.-11:52 p.m.

1 stop18h 07m

C$ 573

St. LouisToronto

STL - YYZ

STLYYZ

Lambert-St Louis

Thu 15/5

7:30 a.m.-10:25 a.m.

Nonstop1h 55m

Toronto Pearson Intl

Sun 18/5

3:00 p.m.-7:58 p.m.

1 stop5h 58m

C$ 593

St. LouisToronto

STL - YYZ

STLYYZ

Lambert-St Louis

Tue 3/6

7:32 a.m.-6:35 p.m.

1 stop10h 03m

Toronto Pearson Intl

Tue 10/6

11:40 a.m.-8:30 p.m.

1 stop9h 50m

C$ 603

St. LouisToronto

STL - YYZ

STLYYZ

Lambert-St Louis

Mon 5/5

5:34 p.m.-11:15 p.m.

1 stop4h 41m

Toronto Pearson Intl

Tue 20/5

7:55 a.m.-8:48 p.m.

1 stop13h 53m

C$ 624

St. LouisMontreal

STL - YUL

STLYUL

Lambert-St Louis

Fri 2/5

1:30 p.m.-5:00 p.m.

Nonstop2h 30m

Montreal Pierre Elliott Trudeau Intl

Sun 4/5

6:10 p.m.-7:58 p.m.

Nonstop2h 48m

C$ 642

St. LouisToronto

STL - YYZ

STLYYZ

Lambert-St Louis

Tue 22/7

6:33 a.m.-2:19 p.m.

2 stops6h 46m

Toronto Pearson Intl

Sat 26/7

2:10 p.m.-3:16 p.m.

Nonstop2h 06m

C$ 649

St. LouisMontreal

STL - YUL

STLYUL

Lambert-St Louis

Tue 27/5

6:00 a.m.-4:04 p.m.

1 stop9h 04m

Montreal Pierre Elliott Trudeau Intl

Wed 28/5

5:00 p.m.-8:07 a.m.

1 stop16h 07m

C$ 652

St. LouisMontreal

STL - YUL

STLYUL

Lambert-St Louis

Wed 11/6

6:04 a.m.-4:45 p.m.

1 stop9h 41m

Montreal Pierre Elliott Trudeau Intl

Tue 17/6

12:30 p.m.-8:30 p.m.

1 stop9h 00m

C$ 678

St. LouisMontreal

STL - YUL

STLYUL

Lambert-St Louis

Wed 28/5

8:15 a.m.-3:49 p.m.

1 stop6h 34m

Montreal Pierre Elliott Trudeau Intl

Wed 28/5

6:10 p.m.-7:58 p.m.

Nonstop2h 48m

C$ 704

Flights are sorted by cheapest round-trip flights first.

Deals found on 16/4

Showing 1-10 of 23 results

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 C$ 167). Flying from St. Louis to Region of Ontario in July is currently the most expensive (average of C$ 258). 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?

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.

Rainfall in Ontario by month

In terms of precipitation, rainfall in Region of Ontario ranges from 51.0 - 83.0 mm per month. June is typically the wettest month, when rainfall can reach 83.0 mm. February is typically the driest time to visit Region of Ontario when rainfall is around 51.0 mm.

Temperature in Ontario by month

If weather is an important factor for your trip to Region of Ontario, use this chart to help with planning. For those seeking warmer temperatures, July is the ideal time of year to visit, when temperatures reach an average of 21.0 C. Travellers hoping to avoid the cold should look outside of January, when temperatures are typically at their lowest (around -6.0 C).

Reviews of airlines servicing Ontario

Read through reviews of airlines operating flights from St. Louis to Ontario, such as Alaska Airlines, Delta and United Airlines. Reviews also offer insight into each airline's entertainment options, comfort, food, crew/service, and boarding process.

Alaska Airlines

8.0

Very good

9,887 reviews

Check prices

Reviews

1 / 20

4.0

Okay

Anonymous,Apr 2025

LAS - STS

flight was delayed both ways even tho the weather was clear >

Alaska Airlines

8.0

Very good

9,887 reviews

Alaska Airlines

8.0

Very good

9,887 reviews

Check prices

Reviews

1 / 20

4.0

Okay

Anonymous,Apr 2025

LAS - STS

flight was delayed both ways even tho the weather was clear >

Delta

8.0

Very good

7,916 reviews

Alaska Airlines

8.0

Very good

9,887 reviews

Check prices

Reviews

1 / 20

4.0

Okay

Anonymous,Apr 2025

LAS - STS

flight was delayed both ways even tho the weather was clear >

United Airlines

7.4

Good

8,667 reviews

Alaska Airlines

8.0

Very good

9,887 reviews

Check prices

Reviews

1 / 20

4.0

Okay

Anonymous,Apr 2025

LAS - STS

flight was delayed both ways even tho the weather was clear >

American Airlines

7.2

Good

10,000 reviews

Alaska Airlines

8.0

Very good

9,887 reviews

Check prices

Reviews

1 / 20

4.0

Okay

Anonymous,Apr 2025

LAS - STS

flight was delayed both ways even tho the weather was clear >

WestJet

7.2

Good

2,809 reviews

Alaska Airlines

8.0

Very good

9,887 reviews

Check prices

Reviews

1 / 20

4.0

Okay

Anonymous,Apr 2025

LAS - STS

flight was delayed both ways even tho the weather was clear >

Related info for your journey

What airport do you fly from for flights from St. Louis to Ontario?
If you book a flight to Ontario from St. Louis, you will be flying from Lambert-St Louis, which is the city’s only airport. Lambert-St Louis (STL) is located 20.4 km from the centre of St. Louis.
What are the cheapest airlines to fly from St. Louis to Region of Ontario one-way?
For one-way options, check prices for American Airlines. According to our data, you can fly for as low as C$ 269. Users have also found prices from C$ 272 and C$ 275 on Delta and Air Canada, respectively.
What are the most popular routes from St. Louis to Region of Ontario?
The most popular flight routes from St. Louis to Region of Ontario are Lambert-St Louis - Montreal Pierre Elliott Trudeau Intl, Lambert-St Louis - Toronto Pearson Intl and Lambert-St Louis - London.
What are the most reliable airlines from St. Louis to Region of Ontario?
Before booking your flight to Region of Ontario from St. Louis, check out the most reliable airlines to get you to your destination on time: Air Canada (78%), Jazz (78%), United Airlines( 78%).
What are the cheapest flights from St. Louis to Region of Ontario?
The cheapest flight price from St. Louis to Region of Ontario is C$ 192. On average you can expect to pay C$ 236. The most popular route, (Lambert-St Louis - Montreal Pierre Elliott Trudeau Intl), can usually be booked for C$ 581.
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 C$ 167). Flying from St. Louis to Region of Ontario in July is currently the most expensive (average of C$ 258). 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

Alternative routes for St. Louis to Ontario

Complete your trip

Region of Ontario car rentals

Toronto Pearson Intl Airport car rentals

Ottawa Airport car rentals

Toronto Island Airport car rentals

Hamilton Airport car rentals

Toronto Region of Waterloo Intl Airport car rentals

London Airport car rentals

Thunder Bay Airport car rentals

Sault Ste Marie Airport car rentals

Timmins Airport car rentals

Kingston Airport car rentals

North Bay Airport car rentals

Direct flights to Canada

Top airline flying from St. Louis to Ontario

Airline	Cheapest	Average	Flexibility	On-time
Air Canada	CheapestC$ 302	AverageC$ 753	FlexibilityNo cancel fee	On-time67%	Search Air Canada flights

Fly with Cheapflights

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

Cheapflights helps you search for flights from St. Louis to Ontario via 900+ travel sites so you don’t have to. After performing a flight search, users can also filter their flight selection by filtering for price, number of stops, airlines, and so on.

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

By finding flights from multiple airlines and providers at completely no cost, Cheapflights helps millions of users like you annually find the best flights to Ontario from St. Louis.

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

Certainly. Search results for flights to Ontario from St. Louis 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 St. Louis to Ontario become cheaper?

Yes! Start tracking prices for St. Louis to Ontario 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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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.

Cheap flights from St. Louis to Ontario from C$ 171

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 9/5. Fares are subject to change and may not be available on all flights or dates of travel.

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 17 April 2025.

Round-trip from

One-way from

Popular in

Cheapest in

Average price

Good one-way deal

Find flight deals from St. Louis to Ontario

Cheapest flights from St. Louis to OntarioExplore 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 17 April 2025.

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 17 April 2025.

Cheapflights Fare Finder

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

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.

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?

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 17 April 2025.

Rainfall in Ontario by month

Plan your trip to Ontario by taking into account the average rainfall totals by month.

Temperature in Ontario by month

Plan your trip to Ontario by taking into account the average temperature totals by month.

Reviews of airlines servicing Ontario

Read through reviews of airlines operating flights from St. Louis to Ontario, such as Alaska Airlines, Delta and United Airlines. Reviews also offer insight into each airline's entertainment options, comfort, food, crew/service, and boarding process.

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?

What are the cheapest airlines to fly from St. Louis to Region of Ontario one-way?

What are the most popular routes from St. Louis to Region of Ontario?

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

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

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

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

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

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

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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 17 April 2025.