$85+ Cheap flights from Ontario to St. Louis (ONT - STL)
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 8/10. Fares are subject to change and may not be available on all flights or dates of travel.
ONT — STL
Jul 4 — Jul 111
Round-trip
1 adult, Economy
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Find cheap flights from Ontario to St. Louis 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 Ontario to St. Louis
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Best
Last-minute
One-way
Cheapest flights from Ontario to St. LouisExplore 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 June 4, 2026.
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 June 4, 2026.
This Kiwi.com deal was found by Cheapflights users on 6/3. 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 8/178:17 am
ONT
- STL
1 stop28h 31m
Frontier
Mon 8/245:33 pm
STL
- ONT
2 stops42h 32m
Frontier
Deal found 6/3![Frontier logo]()
$204
This Kiwi.com deal was found by Cheapflights users on 6/3. 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 8/610:49 am
ONT
- STL
1 stop6h 34m
Frontier
Mon 8/108:08 pm
STL
- ONT
1 stop15h 56m
Frontier
Deal found 6/3![Frontier logo]()
$226
This Kiwi.com deal was found by Cheapflights users on 6/3. 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 8/610:49 am
ONT
- STL
1 stop6h 34m
Frontier
Sun 8/93:41 pm
STL
- ONT
2 stops34h 09m
Frontier
Deal found 6/3![Frontier logo]()
$253
This Kiwi.com deal was found by Cheapflights users on 6/2. 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 7/296:00 am
ONT
- STL
1 stop11h 23m
Frontier
Fri 7/314:57 pm
STL
- ONT
2 stops32h 53m
Frontier
Deal found 6/2![Frontier logo]()
$284
This Kiwi.com deal was found by Cheapflights users on 6/3. 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.
Tue 7/73:40 pm
ONT
- STL
1 stop24h 25m
Frontier
Sun 7/196:34 pm
STL
- ONT
2 stops40h 03m
Frontier
Deal found 6/3![Frontier logo]()
$292
This Booking.com deal was found by Cheapflights users on 6/3. 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 Booking.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 7/73:40 pm
ONT
- STL
1 stop24h 25m
Frontier
Tue 7/148:08 pm
STL
- ONT
1 stop15h 56m
Frontier
Deal found 6/3![Frontier logo]()
$294
This Frontier deal was found by Cheapflights users on 6/1. 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 Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 10/142:58 pm
ONT
- STL
1 stop8h 19m
Frontier
Mon 10/198:10 pm
STL
- ONT
1 stop5h 45m
Frontier
Deal found 6/1![Frontier logo]()
$301
This CheapOair deal was found by Cheapflights users on 6/3. 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 CheapOair is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 7/11:33 pm
ONT
- STL
1 stop19h 45m
Frontier
Tue 7/78:08 pm
STL
- ONT
1 stop15h 56m
Frontier
Deal found 6/3![Frontier logo]()
$302
Best flights from Ontario to St. LouisDiscover carefully curated flight deals from Ontario to St. Louis that have cost, travel time, and layovers in mind to ensure you get the best travel experience. Data last updated June 4, 2026.
Discover carefully curated flight deals from Ontario to St. Louis that have cost, travel time, and layovers in mind to ensure you get the best travel experience. Data last updated June 4, 2026.
This Booking.com deal was found by Cheapflights users on 6/3. 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 Booking.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 7/73:40 pm
ONT
- STL
1 stop24h 25m
Frontier
Sun 7/197:10 pm
STL
- ONT
1 stop22h 44m
Frontier
Deal found 6/3![Frontier logo]()
$307
This United Airlines deal was found by Cheapflights users on 5/31. 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.
Sat 9/121:18 pm
ONT
- STL
1 stop5h 20m
United Airlines
Tue 9/151:36 pm
STL
- ONT
2 stops8h 25m
United Airlines
Deal found 5/31![United Airlines logo]()
$432
This Delta deal was found by Cheapflights users on 6/1. 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.
Sun 9/135:05 pm
ONT
- STL
1 stop5h 31m
Delta
Thu 9/176:55 pm
STL
- ONT
1 stop6h 42m
Delta
Deal found 6/1![Delta logo]()
$441
This Southwest deal was found by Cheapflights users on 6/1. 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 Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 7/284:10 pm
ONT
- STL
1 stop5h 40m
Southwest
Fri 7/312:55 pm
STL
- ONT
2 stops8h 10m
Southwest
Deal found 6/1![Southwest logo]()
$469
This Booking.com deal was found by Cheapflights users on 5/30. 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 Booking.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 7/33:34 pm
ONT
- STL
1 stop20h 32m
Frontier
Tue 7/77:03 pm
STL
- ONT
1 stop15h 00m
Frontier
Deal found 5/30![Frontier logo]()
$333
This Frontier deal was found by Cheapflights users on 5/31. 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 Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 9/129:49 pm
ONT
- STL
1 stop12h 02m
Frontier
Tue 9/1512:46 pm
STL
- ONT
1 stop10h 08m
Frontier
Deal found 5/31![Frontier logo]()
$374
This Delta deal was found by Cheapflights users on 5/31. 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.
Tue 7/285:10 pm
ONT
- STL
1 stop5h 31m
Delta
Wed 7/297:55 pm
STL
- ONT
1 stop5h 53m
Delta
Deal found 5/31![Delta logo]()
$451
This Frontier deal was found by Cheapflights users on 5/30. 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 Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sun 6/146:00 am
ONT
- STL
1 stop10h 53m
Frontier
Thu 6/182:56 pm
STL
- ONT
1 stop6h 55m
Frontier
Deal found 5/30![Frontier logo]()
$390
This Southwest deal was found by Cheapflights users on 6/3. 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 Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sun 9/137:20 am
ONT
- STL
2 stops8h 50m
Southwest
Thu 9/178:25 am
STL
- ONT
1 stop5h 35m
Southwest
Deal found 6/3![Southwest logo]()
$474
This Delta deal was found by Cheapflights users on 5/31. 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.
Mon 7/275:10 pm
ONT
- STL
1 stop5h 31m
Delta
Tue 7/287:55 pm
STL
- ONT
1 stop5h 53m
Delta
Deal found 5/31![Delta logo]()
$464
This Booking.com deal was found by Cheapflights users on 6/3. 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 Booking.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 6/2510:50 am
ONT
- STL
1 stop6h 03m
Frontier
Mon 6/292:56 pm
STL
- ONT
1 stop6h 55m
Frontier
Deal found 6/3![Frontier logo]()
$393
Last-minute flights from Ontario to St. LouisDiscover last-minute flight deals from Ontario to St. Louis. Data last updated June 4, 2026 and is based on user searches.
Discover last-minute flight deals from Ontario to St. Louis. Data last updated June 4, 2026 and is based on user searches.
This CheapOair deal was found by Cheapflights users on 5/31. 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 CheapOair is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 6/241:33 pm
ONT
- STL
1 stop22h 33m
Frontier
Sat 6/272:56 pm
STL
- ONT
1 stop6h 55m
Frontier
Deal found 5/31![Frontier logo]()
$309
This CheapOair deal was found by Cheapflights users on 6/3. 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 CheapOair is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 7/11:33 pm
ONT
- STL
1 stop19h 45m
Frontier
Tue 7/78:08 pm
STL
- ONT
1 stop15h 56m
Frontier
Deal found 6/3![Frontier logo]()
$302
This Booking.com deal was found by Cheapflights users on 6/4. 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 Booking.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 7/11:33 pm
ONT
- STL
1 stop19h 45m
Frontier
Mon 7/67:10 pm
STL
- ONT
1 stop14h 53m
Frontier
Deal found 6/4![Frontier logo]()
$308
This Kiwi.com deal was found by Cheapflights users on 6/3. 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.
Tue 7/73:40 pm
ONT
- STL
1 stop24h 25m
Frontier
Sun 7/196:34 pm
STL
- ONT
2 stops40h 03m
Frontier
Deal found 6/3![Frontier logo]()
$292
This Booking.com deal was found by Cheapflights users on 6/3. 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 Booking.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 7/73:40 pm
ONT
- STL
1 stop24h 25m
Frontier
Tue 7/148:08 pm
STL
- ONT
1 stop15h 56m
Frontier
Deal found 6/3![Frontier logo]()
$294
This Frontier deal was found by Cheapflights users on 6/3. 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 Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 7/106:00 am
ONT
- STL
1 stop11h 23m
Frontier
Tue 7/148:08 pm
STL
- ONT
1 stop5h 42m
Frontier
Deal found 6/3![Frontier logo]()
$314
This Expedia deal was found by Cheapflights users on 6/1. 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 Expedia is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 7/166:00 am
ONT
- STL
1 stop11h 23m
Frontier
Tue 7/218:08 pm
STL
- ONT
1 stop5h 42m
Frontier
Deal found 6/1![Frontier logo]()
$305
This Booking.com deal was found by Cheapflights users on 6/2. 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 Booking.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 7/213:40 pm
ONT
- STL
1 stop24h 25m
Frontier
Sat 7/258:08 pm
STL
- ONT
1 stop15h 56m
Frontier
Deal found 6/2![Frontier logo]()
$306
This Mytrip deal was found by Cheapflights users on 5/31. 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.
Tue 7/213:40 pm
ONT
- STL
1 stop24h 25m
Frontier
Wed 7/298:08 pm
STL
- ONT
1 stop15h 56m
Frontier
Deal found 5/31![Frontier logo]()
$310
This Kiwi.com deal was found by Cheapflights users on 6/2. 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 7/296:00 am
ONT
- STL
1 stop11h 23m
Frontier
Fri 7/314:57 pm
STL
- ONT
2 stops32h 53m
Frontier
Deal found 6/2![Frontier logo]()
$284
One-way flights from Ontario to St. LouisSearch for one-way flight options from Ontario to St. Louis. Find affordable one-way fares based on user searches. Data last updated June 4, 2026.
Search for one-way flight options from Ontario to St. Louis. Find affordable one-way fares based on user searches. Data last updated June 4, 2026.
This Trip.com deal was found by Cheapflights users on 6/3. 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 Trip.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 8/106:00 am
ONT
- STL
1 stop11h 23m
Frontier
Deal found 6/3![Frontier logo]()
$85
This Trip.com deal was found by Cheapflights users on 6/3. 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 Trip.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 7/306:00 am
ONT
- STL
1 stop11h 23m
Frontier
Deal found 6/3![Frontier logo]()
$119
This Trip.com deal was found by Cheapflights users on 6/3. 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 Trip.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 8/36:00 am
ONT
- STL
1 stop11h 23m
Frontier
Deal found 6/3![Frontier logo]()
$121
This Trip.com deal was found by Cheapflights users on 5/31. 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 Trip.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 9/26:00 am
ONT
- STL
1 stop11h 23m
Frontier
Deal found 5/31![Frontier logo]()
$127
This iWofly deal was found by Cheapflights users on 6/2. 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 iWofly is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 8/1210:49 am
ONT
- STL
1 stop6h 34m
Frontier
Deal found 6/2![Frontier logo]()
$144
This Frontier deal was found by Cheapflights users on 6/2. 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 Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 7/2810:49 am
ONT
- STL
1 stop6h 34m
Frontier
Deal found 6/2![Frontier logo]()
$146
This Super.com deal was found by Cheapflights users on 6/4. 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 Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 7/11:33 pm
ONT
- STL
1 stop19h 45m
Frontier
Deal found 6/4![Frontier logo]()
$150
This Super.com deal was found by Cheapflights users on 6/2. 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 Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 6/231:33 pm
ONT
- STL
1 stop27h 18m
Frontier
Deal found 6/2![Frontier logo]()
$151
This Booking.com deal was found by Cheapflights users on 6/4. 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 Booking.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 6/301:33 pm
ONT
- STL
1 stop27h 18m
Frontier
Deal found 6/4![Frontier logo]()
$153
This CheapOair deal was found by Cheapflights users on 5/31. 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 CheapOair is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 9/239:49 pm
ONT
- STL
1 stop12h 02m
Frontier
Deal found 5/31![Frontier logo]()
$157
Find flight deals from Ontario to St. Louis
Discover tips and strategies to find the most affordable flight options for your journey from Ontario (ONT) to St. Louis (STL). Learn about various techniques such as flexible date searches, comparing prices across and setting up price alerts. Use these methods to find the cheapest flights available for your travel needs. Data last updated June 4, 2026.
Most accurate provider | FlightHub 3 stars |
|---|---|
Most trusted provider | FlightHub 3 stars |
Round-trip from | $204 (Kiwi.com) |
One-way from | $85 (Trip.com) |
Popular in | December |
Cheapest in | September |
Average price | $353 |
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 2,558,603 searches. Data last updated June 4, 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
Cheapest round-trip
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
Tue 7/7
3:40 pm-6:05 pm
1 stop24h 25m
Lambert-St Louis
Sun 7/19
7:10 pm-3:54 pm
1 stop22h 44m
$307
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
Fri 7/3
3:34 pm-2:06 pm
1 stop20h 32m
Lambert-St Louis
Tue 7/7
7:03 pm-8:03 am
1 stop15h 00m
$333
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
Sat 9/12
9:49 pm-11:51 am
1 stop12h 02m
Lambert-St Louis
Tue 9/15
12:46 pm-8:54 pm
1 stop10h 08m
$374
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
Sun 6/14
6:00 am-6:53 pm
1 stop10h 53m
Lambert-St Louis
Thu 6/18
2:56 pm-7:51 pm
1 stop6h 55m
$390
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
Thu 6/25
10:50 am-6:53 pm
1 stop6h 03m
Lambert-St Louis
Mon 6/29
2:56 pm-7:51 pm
1 stop6h 55m
$393
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
Sat 9/12
1:18 pm-8:38 pm
1 stop5h 20m
Lambert-St Louis
Tue 9/15
1:36 pm-8:01 pm
2 stops8h 25m
$432
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
Sun 9/13
5:05 pm-12:36 am
1 stop5h 31m
Lambert-St Louis
Thu 9/17
6:55 pm-11:37 pm
1 stop6h 42m
$441
Quickest round-trip
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
Tue 7/28
5:10 pm-12:41 am
1 stop5h 31m
Lambert-St Louis
Wed 7/29
7:55 pm-11:48 pm
1 stop5h 53m
$451
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
Mon 7/27
5:10 pm-12:41 am
1 stop5h 31m
Lambert-St Louis
Tue 7/28
7:55 pm-11:48 pm
1 stop5h 53m
$464
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
Tue 7/28
4:10 pm-11:50 pm
1 stop5h 40m
Lambert-St Louis
Fri 7/31
2:55 pm-9:05 pm
2 stops8h 10m
$469
Showing 1-10 of 22 resultsSorted by cheapest first
Compare providers for flights from Ontario to St. Louis
Provider information is updated monthly. Please note that these providers often have deals for this flight, but the availability may vary on a day-by-day basis on Cheapflights.
Use the table below to compare price accuracy, trust ratings, and cancellation policies for each provider offering flight deals from Ontario to St. Louis in June.
| Provider | Price Accuracy | Trust Score* |
|---|---|---|
| Price Accuracy1 star | Trust Score*3 stars | |
| Price Accuracy3 stars | Trust Score*3 stars | |
| Price Accuracy2 stars | Trust Score*3 stars | |
| Price Accuracy- | Trust Score*1 star |
- Most accurate provider: When it comes to deals on Ontario-St. Louis flights, users find the pricing of FlightHub to be most consistent on Cheapflights vs. FlightHub Users can find the same prices on Ontario-St. Louis flight deals on Cheapflights vs. FlightHub >95% of the time. Price accuracy is based on data collected from Ontario-St. Louis flight searches over the past month and is updated monthly.
- Most trusted provider: When it comes to deals on Ontario-St. Louis flights, Cheapflights users trust FlightHub the most. FlightHub has received a user feedback score of 3 out of 3 stars (3 being the best), meaning they have been trusted the most by Cheapflights users looking for Ontario-St. Louis flight deals. Provider user feedback score is based on Cheapflights searches over the past month and is updated monthly.
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.
ONT-STL
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
Prices
More
How far ahead should I book a flight from Ontario to St. Louis?
The best time to book flights from Ontario to St. Louis is 81 days before your desired departure date. The cost of your flight will likely increase significantly if you book two weeks in advance of your flight.
What is the cheapest month to book a flight from Ontario to St. Louis?
Currently, September is the cheapest month in which you can book a flight from Ontario to St. Louis (average of $247). Flying from Ontario to St. Louis in December is currently the most expensive (average of $426). 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.
How much does it cost to fly round-trip from Ontario to St. Louis?
What’s the top layover airport for flights from Ontario to St. Louis?
Share of 1-stop round-trip flights from Ontario to St. Louis chosen by Cheapflights users in the past 12 months, using the same layover each way.
Las Vegas (LAS) – chosen by Cheapflights users on 67% of 1-stop itineraries from Ontario to St. Louis on Cheapflights.
What’s the cheapest layover airport for flights from Ontario to St. Louis?
Average round-trip fare for 1-stop flights from Ontario to St. Louis, chosen by Cheapflights users in the past 12 months, with the same layover each way.
Las Vegas (LAS) is the most affordable 1-stop option, with an average round-trip price of $413.
What’s the fastest layover option from Ontario to St. Louis?
Shortest average travel time for 1-stop one-way flights from Ontario to St. Louis, based on itineraries clicked by Cheapflights users over the past 12 months, grouped by layover airport.
Flights via Denver (DEN) have the shortest average one-way travel time for 1-stop routes: 5h 10m.
Which airport typically offers the quickest layover for flights from Ontario to St. Louis?
Average layover duration for 1-stop one-way flights from Ontario to St. Louis, chosen by Cheapflights users in the last 12 months, grouped by stopover airport.
Flights via Denver (DEN) offer the fastest connection on this route, with an average layover time of 0h 55m.
Reviews of airlines servicing St. Louis
Get insights into the airlines that provide service to St. Louis. 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 St. Louis. Reviews last updated June 4, 2026.
Get a feel of what it's like to fly with Southwest,Delta, andUnited Airlines from Ontario to St. Louis by reading reviews from past customers. Users have also rated airlines in terms of entertainment options, comfort, food, crew/service, and boarding process.
Food
7.0
Comfort
8.0
Entertainment
7.5
Crew
8.6
Overall
8.0
Boarding
8.1
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Food
7.0
Comfort
8.0
Entertainment
7.5
Crew
8.6
Overall
8.0
Boarding
8.1
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Food
7.0
Comfort
8.0
Entertainment
7.5
Crew
8.6
Overall
8.0
Boarding
8.1
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Food
7.0
Comfort
8.0
Entertainment
7.5
Crew
8.6
Overall
8.0
Boarding
8.1
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Food
7.0
Comfort
8.0
Entertainment
7.5
Crew
8.6
Overall
8.0
Boarding
8.1
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Food
7.0
Comfort
8.0
Entertainment
7.5
Crew
8.6
Overall
8.0
Boarding
8.1
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
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.
Traveling to a place near St. Louis?
Book flights to St. Louis if you plan to visit one of these locationsO'Fallon
Edwardsville
Fenton
Swansea
Fairview Heights
Maryland Heights
Collinsville
Eureka
Wentzville
Glencoe
Chesterfield
Alton
Farmington
Festus
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Ontario and St. Louis flights
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Top 5 airlines flying from Ontario to St. Louis
Discover the top 5 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 2,558,603 searches. Data last updated June 4, 2026.
| Airline | Cheapest | Average | Flexibility | On-time |
|---|---|---|---|---|
| Cheapest$139 | Average$420 | FlexibilityNo cancel fee | On-timeN/A | |
| Cheapest$160 | Average$251 | FlexibilityNo cancel fee | On-time62% | |
| Cheapest$249 | Average$506 | FlexibilityNo cancel fee | On-time69% | |
| Cheapest$292 | Average$399 | FlexibilityNo cancel fee | On-time71% | |
| Cheapest$316 | Average$497 | FlexibilityNo cancel fee | On-time63% |