$67+ 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 4/24. Fares are subject to change and may not be available on all flights or dates of travel.
ONT — STL
Mar 28 — Apr 41
1 adult, Economy
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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
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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 February 26, 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 February 26, 2026.
This Kiwi.com deal was found by Cheapflights users on 2/25. 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 4/96:20 am
ONT
- STL
1 stop25h 28m
Frontier
Mon 4/138:19 pm
STL
- ONT
1 stop29h 36m
Frontier
Deal found 2/25![Frontier logo]()
$163
This Expedia deal was found by Cheapflights users on 2/25. 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 4/2312:59 am
ONT
- STL
1 stop16h 22m
Frontier
Sun 4/269:55 pm
STL
- ONT
1 stop12h 29m
Frontier
Deal found 2/25![Frontier logo]()
$190
This Booking.com deal was found by Cheapflights users on 2/23. 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 4/227:44 pm
ONT
- STL
1 stop23h 16m
Frontier
Mon 4/273:21 pm
STL
- ONT
1 stop10h 27m
Frontier
Deal found 2/23![Frontier logo]()
$191
This Booking.com deal was found by Cheapflights users on 2/23. 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 4/1611:47 am
ONT
- STL
1 stop7h 13m
Frontier
Sat 4/188:17 pm
STL
- ONT
1 stop13h 09m
Frontier
Deal found 2/23![Frontier logo]()
$197
This CheapOair deal was found by Cheapflights users on 2/23. 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.
Thu 4/3012:59 am
ONT
- STL
1 stop16h 22m
Frontier
Sun 5/39:55 pm
STL
- ONT
1 stop24h 09m
Frontier
Deal found 2/23![Frontier logo]()
$201
This Booking.com deal was found by Cheapflights users on 2/23. 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 4/157:44 pm
ONT
- STL
1 stop23h 16m
Frontier
Sun 4/199:55 pm
STL
- ONT
1 stop14h 19m
Frontier
Deal found 2/23![Frontier logo]()
$203
This Kiwi.com deal was found by Cheapflights users on 2/25. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 4/106:20 am
ONT
- STL
1 stop25h 28m
Frontier
Mon 4/138:19 pm
STL
- ONT
1 stop29h 36m
Frontier
Deal found 2/25![Frontier logo]()
$207
This Jetabroad deal was found by Cheapflights users on 2/22. 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 Jetabroad is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sun 4/2612:59 am
ONT
- STL
1 stop16h 33m
Frontier
Sat 5/28:17 pm
STL
- ONT
1 stop13h 09m
Frontier
Deal found 2/22![Frontier logo]()
$210
This Expedia deal was found by Cheapflights users on 2/24. 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.
Wed 4/1512:59 am
ONT
- STL
1 stop16h 22m
Frontier
Mon 4/209:55 pm
STL
- ONT
1 stop14h 49m
Frontier
Deal found 2/24![Frontier logo]()
$211
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 February 26, 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 February 26, 2026.
This CheapOair deal was found by Cheapflights users on 2/22. 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.
Thu 5/78:59 pm
ONT
- STL
1 stop22h 01m
Frontier
Sun 5/109:55 pm
STL
- ONT
1 stop12h 09m
Frontier
Deal found 2/22![Frontier logo]()
$201
This Alaska Airlines deal was found by Cheapflights users on 2/22. 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 Alaska Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 3/166:14 am
ONT
- STL
1 stop29h 37m
Alaska Airlines
Tue 4/73:50 pm
STL
- ONT
1 stop10h 09m
Alaska Airlines
Deal found 2/22![Alaska Airlines logo]()
$363
This Delta deal was found by Cheapflights users on 2/22. 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 4/2610:15 pm
ONT
- STL
1 stop8h 15m
Delta
Sat 5/211:42 am
STL
- ONT
1 stop8h 51m
Delta
Deal found 2/22![Delta logo]()
$370
This United Airlines deal was found by Cheapflights users on 2/23. 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 4/15:10 am
ONT
- STL
1 stop5h 58m
United Airlines
Tue 4/74:30 pm
STL
- ONT
1 stop6h 06m
United Airlines
Deal found 2/23![United Airlines logo]()
$380
This Delta deal was found by Cheapflights users on 2/22. 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 4/286:00 am
ONT
- STL
1 stop5h 23m
Delta
Sun 5/36:00 am
STL
- ONT
1 stop7h 36m
Delta
Deal found 2/22![Delta logo]()
$370
This United Airlines deal was found by Cheapflights users on 2/25. 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.
Thu 4/236:49 pm
ONT
- STL
2 stops11h 36m
United Airlines
Fri 4/242:40 pm
STL
- ONT
2 stops10h 05m
United Airlines
Deal found 2/25![United Airlines logo]()
$429
This Alaska Airlines deal was found by Cheapflights users on 2/24. 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 Alaska Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 7/77:00 am
ONT
- STL
1 stop7h 33m
Alaska Airlines
Thu 7/95:33 pm
STL
- ONT
1 stop8h 21m
Alaska Airlines
Deal found 2/24![Alaska Airlines logo]()
$437
This Delta deal was found by Cheapflights users on 2/26. 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 3/2910:25 pm
ONT
- STL
1 stop8h 40m
Delta
Thu 4/96:12 pm
STL
- ONT
1 stop7h 39m
Delta
Deal found 2/26![Delta logo]()
$428
This Alaska Airlines deal was found by Cheapflights users on 2/22. 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 Alaska Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 5/287:00 am
ONT
- STL
1 stop7h 37m
Alaska Airlines
Sat 5/305:33 pm
STL
- ONT
1 stop8h 23m
Alaska Airlines
Deal found 2/22![Alaska Airlines logo]()
$437
This United Airlines deal was found by Cheapflights users on 2/26. 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 5/210:43 am
ONT
- STL
2 stops10h 21m
United Airlines
Fri 5/82:35 pm
STL
- ONT
2 stops10h 24m
United Airlines
Deal found 2/26![United Airlines logo]()
$437
This Delta deal was found by Cheapflights users on 2/24. 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 7/610:59 pm
ONT
- STL
1 stop7h 08m
Delta
Wed 7/156:59 pm
STL
- ONT
1 stop6h 45m
Delta
Deal found 2/24![Delta logo]()
$437
Last-minute flights from Ontario to St. LouisDiscover last-minute flight deals from Ontario to St. Louis. Data last updated February 26, 2026 and is based on user searches.
Discover last-minute flight deals from Ontario to St. Louis. Data last updated February 26, 2026 and is based on user searches.
This Booking.com deal was found by Cheapflights users on 2/22. 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.
Mon 3/99:40 pm
ONT
- STL
1 stop19h 31m
Frontier
Wed 3/118:12 pm
STL
- ONT
1 stop5h 47m
Frontier
Deal found 2/22![Frontier logo]()
$237
This CheapOair deal was found by Cheapflights users on 2/24. 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.
Fri 3/133:30 pm
ONT
- STL
1 stop17h 49m
Frontier
Tue 3/178:06 pm
STL
- ONT
1 stop19h 22m
Frontier
Deal found 2/24![Frontier logo]()
$241
This Mytrip deal was found by Cheapflights users on 2/23. 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.
Sat 3/147:31 pm
ONT
- STL
1 stop14h 59m
Frontier
Wed 3/188:12 pm
STL
- ONT
1 stop5h 47m
Frontier
Deal found 2/23![Frontier logo]()
$236
This CheapOair deal was found by Cheapflights users on 2/24. 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.
Sat 3/142:23 pm
ONT
- STL
1 stop20h 07m
Frontier
Thu 3/198:06 pm
STL
- ONT
1 stop21h 31m
Frontier
Deal found 2/24![Frontier logo]()
$265
This Booking.com deal was found by Cheapflights users on 2/26. 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 3/172:23 pm
ONT
- STL
1 stop18h 56m
Frontier
Fri 3/208:12 pm
STL
- ONT
1 stop5h 47m
Frontier
Deal found 2/26![Frontier logo]()
$248
This CheapOair deal was found by Cheapflights users on 2/23. 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.
Mon 3/2311:17 am
ONT
- STL
1 stop22h 02m
Frontier
Mon 3/308:12 pm
STL
- ONT
1 stop5h 47m
Frontier
Deal found 2/23![Frontier logo]()
$244
This Booking.com deal was found by Cheapflights users on 2/25. 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 3/242:23 pm
ONT
- STL
1 stop18h 56m
Frontier
Wed 4/18:16 pm
STL
- ONT
1 stop5h 40m
Frontier
Deal found 2/25![Frontier logo]()
$218
This CheapOair deal was found by Cheapflights users on 2/25. 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.
Tue 3/242:23 pm
ONT
- STL
1 stop18h 56m
Frontier
Thu 3/268:06 pm
STL
- ONT
1 stop14h 00m
Frontier
Deal found 2/25![Frontier logo]()
$225
This CheapOair deal was found by Cheapflights users on 2/25. 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.
Tue 3/242:23 pm
ONT
- STL
1 stop18h 56m
Frontier
Fri 3/278:12 pm
STL
- ONT
1 stop5h 47m
Frontier
Deal found 2/25![Frontier logo]()
$231
This Booking.com deal was found by Cheapflights users on 2/24. 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 3/276:15 am
ONT
- STL
1 stop25h 34m
Frontier
Wed 4/18:16 pm
STL
- ONT
1 stop5h 40m
Frontier
Deal found 2/24![Frontier logo]()
$264
This Frontier deal was found by Cheapflights users on 2/26. 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.
Mon 3/309:49 pm
ONT
- STL
1 stop11h 30m
Frontier
Wed 4/18:16 pm
STL
- ONT
1 stop5h 40m
Frontier
Deal found 2/26![Frontier logo]()
$235
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 February 26, 2026.
Search for one-way flight options from Ontario to St. Louis. Find affordable one-way fares based on user searches. Data last updated February 26, 2026.
This Kiwi.com deal was found by Cheapflights users on 2/25. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 4/2412:59 am
ONT
- STL
1 stop16h 33m
Frontier
Deal found 2/25![Frontier logo]()
$67
This Super.com deal was found by Cheapflights users on 2/22. 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.
Fri 5/156:15 am
ONT
- STL
1 stop5h 57m
Frontier
Deal found 2/22![Frontier logo]()
$94
This Super.com deal was found by Cheapflights users on 2/23. 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.
Sun 4/126:20 am
ONT
- STL
1 stop25h 28m
Frontier
Deal found 2/23![Frontier logo]()
$99
This Super.com deal was found by Cheapflights users on 2/25. 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 4/297:44 pm
ONT
- STL
1 stop23h 16m
Frontier
Deal found 2/25![Frontier logo]()
$100
This Booking.com deal was found by Cheapflights users on 2/23. 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.
Sun 4/1912:59 am
ONT
- STL
1 stop16h 33m
Frontier
Deal found 2/23![Frontier logo]()
$101
This Trip.com deal was found by Cheapflights users on 2/23. 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 3/2311:17 am
ONT
- STL
1 stop22h 02m
Frontier
Deal found 2/23![Frontier logo]()
$104
This CheapOair deal was found by Cheapflights users on 2/24. 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.
Thu 5/712:59 am
ONT
- STL
1 stop16h 13m
Frontier
Deal found 2/24![Frontier logo]()
$107
This Kiwi.com deal was found by Cheapflights users on 2/23. 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.
Sun 3/151:55 pm
ONT
- STL
2 stops17h 54m
Frontier
Deal found 2/23![Frontier logo]()
$113
This Kiwi.com deal was found by Cheapflights users on 2/25. 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 3/268:07 am
ONT
- STL
1 stop25h 12m
Frontier
Deal found 2/25![Frontier logo]()
$119
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 February 26, 2026.
Most accurate provider | FlightHub 3 stars |
|---|---|
Most trusted provider | FlightHub 3 stars |
Round-trip from | $163 (Kiwi.com) |
One-way from | $67 (Kiwi.com) |
Popular in | December |
Cheapest in | September |
Average price | $352 |
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 February 26, 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
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
Thu 5/7
8:59 pm-9:00 pm
1 stop22h 01m
Lambert-St Louis
Sun 5/10
9:55 pm-8:04 am
1 stop12h 09m
$201
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
Mon 3/16
6:14 am-1:51 pm
1 stop29h 37m
Lambert-St Louis
Tue 4/7
3:50 pm-11:59 pm
1 stop10h 09m
$363
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
Sun 4/26
10:15 pm-8:30 am
1 stop8h 15m
Lambert-St Louis
Sat 5/2
11:42 am-6:33 pm
1 stop8h 51m
$370
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
Tue 4/28
6:00 am-1:23 pm
1 stop5h 23m
Lambert-St Louis
Sun 5/3
6:00 am-11:36 am
1 stop7h 36m
$370
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
Wed 4/1
5:10 am-1:08 pm
1 stop5h 58m
Lambert-St Louis
Tue 4/7
4:30 pm-8:36 pm
1 stop6h 06m
$380
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
Sun 3/29
10:25 pm-9:05 am
1 stop8h 40m
Lambert-St Louis
Thu 4/9
6:12 pm-11:51 pm
1 stop7h 39m
$428
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
Thu 4/23
6:49 pm-8:25 am
2 stops11h 36m
Lambert-St Louis
Fri 4/24
2:40 pm-10:45 pm
2 stops10h 05m
$429
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
Tue 7/7
7:00 am-4:33 pm
1 stop7h 33m
Lambert-St Louis
Thu 7/9
5:33 pm-11:54 pm
1 stop8h 21m
$437
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
Thu 5/28
7:00 am-4:37 pm
1 stop7h 37m
Lambert-St Louis
Sat 5/30
5:33 pm-11:56 pm
1 stop8h 23m
$437
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
Sat 5/2
10:43 am-11:04 pm
2 stops10h 21m
Lambert-St Louis
Fri 5/8
2:35 pm-10:59 pm
2 stops10h 24m
$437
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 February.
| Provider | Price Accuracy | Trust Score* |
|---|---|---|
| Price Accuracy1 star | Trust Score*3 stars | |
| Price Accuracy3 stars | Trust Score*3 stars | |
| Price Accuracy3 stars | Trust Score*3 stars | |
| Price Accuracy- | Trust Score*1 star | |
| Price Accuracy3 stars | Trust Score*3 stars | |
| Price Accuracy2 stars | Trust Score*3 stars | |
| Price Accuracy1 star | Trust Score*3 stars |
- 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
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How far ahead should I book a flight from Ontario to St. Louis?
Use this chart to determine the optimal time to book a round-trip flight from Ontario to St. Louis. Price data was last updated on February 20, 2026.
The best time to book flights from Ontario to St. Louis is 82 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 $71). Flying from Ontario to St. Louis in March is currently the most expensive (average of $226). 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’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 71% 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 $328.
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 Phoenix (PHX) have the shortest average one-way travel time for 1-stop routes: 5h 35m.
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 Phoenix (PHX) offer the fastest connection on this route, with an average layover time of 1h 09m.
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 February 26, 2026.
Get a feel of what it's like to fly with Southwest, Delta, and United 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.
Comfort
8.0
Boarding
8.1
Entertainment
7.5
Food
7.0
Overall
8.0
Crew
8.6
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Comfort
8.0
Boarding
8.1
Entertainment
7.5
Food
7.0
Overall
8.0
Crew
8.6
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Comfort
8.0
Boarding
8.1
Entertainment
7.5
Food
7.0
Overall
8.0
Crew
8.6
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Comfort
8.0
Boarding
8.1
Entertainment
7.5
Food
7.0
Overall
8.0
Crew
8.6
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Comfort
8.0
Boarding
8.1
Entertainment
7.5
Food
7.0
Overall
8.0
Crew
8.6
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Comfort
8.0
Boarding
8.1
Entertainment
7.5
Food
7.0
Overall
8.0
Crew
8.6
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 locationsEdwardsville
O'Fallon
Swansea
Fairview Heights
Fenton
Maryland Heights
Collinsville
Eureka
Wentzville
Glencoe
Chesterfield
Alton
Farmington
Festus
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Ontario and St. Louis flights
Browse other Ontario and St. Louis flight options. Last updated on February 26, 2026.
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Other flights to St. Louis
Explore flights to St. Louis departing from other origins. Flights are based on user searches made on Cheapflights and were last updated on February 26, 2026.
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 February 26, 2026.
| Airline | Cheapest | Average | Flexibility | On-time |
|---|---|---|---|---|
| Cheapest$139 | Average$391 | FlexibilityNo cancel fee | On-timeN/A | |
| Cheapest$146 | Average$229 | FlexibilityNo cancel fee | On-time62% | |
| Cheapest$292 | Average$471 | FlexibilityNo cancel fee | On-time69% | |
| Cheapest$292 | Average$396 | FlexibilityNo cancel fee | On-time71% | |
| Cheapest$340 | Average$427 | FlexibilityNo cancel fee | On-time63% |