$79+ 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 5/23. Fares are subject to change and may not be available on all flights or dates of travel.
ONT — STL
May 22 — May 291
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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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 April 22, 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 April 22, 2026.
This Frontier deal was found by Cheapflights users on 4/17. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 5/88:44 am
ONT
- STL
1 stop9h 39m
Frontier
Sun 5/1012:36 pm
STL
- ONT
1 stop8h 56m
Frontier
Deal found 4/17![Frontier logo]()
$160
This Booking.com deal was found by Cheapflights users on 4/20. 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 5/144:04 pm
ONT
- STL
1 stop26h 19m
Frontier
Tue 5/196:51 pm
STL
- ONT
1 stop22h 53m
Frontier
Deal found 4/20![Frontier logo]()
$162
This Trip.com deal was found by Cheapflights users on 4/17. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Trip.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 5/96:00 am
ONT
- STL
1 stop11h 23m
Frontier
Tue 5/126:51 pm
STL
- ONT
1 stop22h 53m
Frontier
Deal found 4/17![Frontier logo]()
$163
This CheapOair deal was found by Cheapflights users on 4/18. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure CheapOair is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 5/1111:36 am
ONT
- STL
1 stop28h 30m
Frontier
Fri 5/159:18 pm
STL
- ONT
1 stop24h 14m
Frontier
Deal found 4/18![Frontier logo]()
$171
This Frontier deal was found by Cheapflights users on 4/21. 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 5/118:44 am
ONT
- STL
1 stop9h 39m
Frontier
Thu 5/1412:36 pm
STL
- ONT
1 stop8h 56m
Frontier
Deal found 4/21![Frontier logo]()
$180
This CheapOair deal was found by Cheapflights users on 4/21. 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 5/194:39 pm
ONT
- STL
1 stop23h 27m
Frontier
Wed 6/36:51 pm
STL
- ONT
1 stop22h 18m
Frontier
Deal found 4/21![Frontier logo]()
$185
This Booking.com deal was found by Cheapflights users on 4/20. 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 5/2210:50 am
ONT
- STL
1 stop6h 33m
Frontier
Tue 6/238:08 pm
STL
- ONT
1 stop5h 41m
Frontier
Deal found 4/20![Frontier logo]()
$186
This Booking.com deal was found by Cheapflights users on 4/21. 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 5/134:39 pm
ONT
- STL
1 stop17h 02m
Frontier
Sun 5/1712:36 pm
STL
- ONT
1 stop21h 13m
Frontier
Deal found 4/21![Frontier logo]()
$187
This Super.com deal was found by Cheapflights users on 4/20. 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.
Mon 5/412:22 pm
ONT
- STL
1 stop27h 44m
Frontier
Tue 5/196:51 pm
STL
- ONT
1 stop22h 53m
Frontier
Deal found 4/20![Frontier logo]()
$191
This CheapOair deal was found by Cheapflights users on 4/21. 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 5/144:04 pm
ONT
- STL
1 stop26h 19m
Frontier
Sun 5/1712:36 pm
STL
- ONT
1 stop21h 13m
Frontier
Deal found 4/21![Frontier logo]()
$196
This Booking.com deal was found by Cheapflights users on 4/19. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Booking.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 5/1811:36 am
ONT
- STL
1 stop28h 30m
Frontier
Mon 5/259:06 pm
STL
- ONT
1 stop12h 58m
Frontier
Deal found 4/19![Frontier logo]()
$198
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 April 22, 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 April 22, 2026.
This Super.com deal was found by Cheapflights users on 4/17. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 5/2810:50 am
ONT
- STL
1 stop6h 33m
Frontier
Sun 5/319:06 pm
STL
- ONT
1 stop20h 03m
Frontier
Deal found 4/17![Frontier logo]()
$213
This Alaska Airlines deal was found by Cheapflights users on 4/22. 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.
Tue 9/227:10 am
ONT
- STL
1 stop7h 53m
Alaska Airlines
Wed 9/303:17 pm
STL
- ONT
1 stop10h 07m
Alaska Airlines
Deal found 4/22![Alaska Airlines logo]()
$341
This Expedia deal was found by Cheapflights users on 4/17. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Expedia is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 5/2111:51 am
ONT
- STL
1 stop6h 20m
Multiple Airlines
Tue 5/265:33 pm
STL
- ONT
2 stops19h 39m
Multiple Airlines
Deal found 4/17![Multiple Airlines logo]()
$404
This Delta deal was found by Cheapflights users on 4/21. 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 5/2510:00 pm
ONT
- STL
1 stop9h 44m
Delta
Mon 6/17:59 pm
STL
- ONT
1 stop5h 35m
Delta
Deal found 4/21![Delta logo]()
$423
This United Airlines deal was found by Cheapflights users on 4/20. 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.
Sun 9/139:01 am
ONT
- STL
1 stop7h 23m
United Airlines
Thu 9/175:10 am
STL
- ONT
2 stops9h 02m
United Airlines
Deal found 4/20![United Airlines logo]()
$428
This American Airlines deal was found by Cheapflights users on 4/17. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure American Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 5/136:15 am
ONT
- STL
2 stops9h 06m
American Airlines
Sat 5/1612:27 pm
STL
- ONT
2 stops9h 07m
American Airlines
Deal found 4/17![American Airlines logo]()
$460
This Southwest deal was found by Cheapflights users on 4/20. 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 9/178:30 am
STL
- ONT
2 stops7h 30m
Southwest
Deal found 4/20![Southwest logo]()
$464
This Kiwi.com deal was found by Cheapflights users on 4/17. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 5/134:39 pm
ONT
- STL
1 stop17h 02m
Frontier
Sat 5/167:08 pm
STL
- ONT
2 stops26h 24m
Frontier
Deal found 4/17![Frontier logo]()
$382
This Delta deal was found by Cheapflights users on 4/18. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 5/296:45 am
ONT
- STL
2 stops10h 18m
Delta
Tue 6/27:59 pm
STL
- ONT
1 stop5h 35m
Delta
Deal found 4/18![Delta logo]()
$441
This Alaska Airlines deal was found by Cheapflights users on 4/20. 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.
Wed 5/136:00 am
ONT
- STL
1 stop10h 45m
Alaska Airlines
Sat 5/165:33 pm
STL
- ONT
1 stop8h 23m
Alaska Airlines
Deal found 4/20![Alaska Airlines logo]()
$450
This Frontier deal was found by Cheapflights users on 4/17. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sun 7/1910:50 am
ONT
- STL
1 stop6h 33m
Frontier
Wed 7/228:08 pm
STL
- ONT
1 stop5h 41m
Frontier
Deal found 4/17![Frontier logo]()
$420
This Alaska Airlines deal was found by Cheapflights users on 4/17. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Alaska Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 9/237:10 am
ONT
- STL
1 stop7h 53m
Alaska Airlines
Sat 10/33:24 pm
STL
- ONT
1 stop9h 15m
Alaska Airlines
Deal found 4/17![Alaska Airlines logo]()
$477
Last-minute flights from Ontario to St. LouisDiscover last-minute flight deals from Ontario to St. Louis. Data last updated April 22, 2026 and is based on user searches.
Discover last-minute flight deals from Ontario to St. Louis. Data last updated April 22, 2026 and is based on user searches.
This Super.com deal was found by Cheapflights users on 4/20. 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.
Mon 5/412:22 pm
ONT
- STL
1 stop27h 44m
Frontier
Tue 5/196:51 pm
STL
- ONT
1 stop22h 53m
Frontier
Deal found 4/20![Frontier logo]()
$191
This Frontier deal was found by Cheapflights users on 4/17. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 5/88:44 am
ONT
- STL
1 stop9h 39m
Frontier
Sun 5/1012:36 pm
STL
- ONT
1 stop8h 56m
Frontier
Deal found 4/17![Frontier logo]()
$160
This Trip.com deal was found by Cheapflights users on 4/17. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Trip.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 5/96:00 am
ONT
- STL
1 stop11h 23m
Frontier
Tue 5/126:51 pm
STL
- ONT
1 stop22h 53m
Frontier
Deal found 4/17![Frontier logo]()
$163
This CheapOair deal was found by Cheapflights users on 4/18. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure CheapOair is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 5/1111:36 am
ONT
- STL
1 stop28h 30m
Frontier
Fri 5/159:18 pm
STL
- ONT
1 stop24h 14m
Frontier
Deal found 4/18![Frontier logo]()
$171
This Frontier deal was found by Cheapflights users on 4/21. 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 5/118:44 am
ONT
- STL
1 stop9h 39m
Frontier
Thu 5/1412:36 pm
STL
- ONT
1 stop8h 56m
Frontier
Deal found 4/21![Frontier logo]()
$180
This Booking.com deal was found by Cheapflights users on 4/21. 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 5/134:39 pm
ONT
- STL
1 stop17h 02m
Frontier
Sun 5/1712:36 pm
STL
- ONT
1 stop21h 13m
Frontier
Deal found 4/21![Frontier logo]()
$187
This Booking.com deal was found by Cheapflights users on 4/20. 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 5/144:04 pm
ONT
- STL
1 stop26h 19m
Frontier
Tue 5/196:51 pm
STL
- ONT
1 stop22h 53m
Frontier
Deal found 4/20![Frontier logo]()
$162
This CheapOair deal was found by Cheapflights users on 4/21. 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 5/144:04 pm
ONT
- STL
1 stop26h 19m
Frontier
Sun 5/1712:36 pm
STL
- ONT
1 stop21h 13m
Frontier
Deal found 4/21![Frontier logo]()
$196
This Booking.com deal was found by Cheapflights users on 4/19. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Booking.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 5/1811:36 am
ONT
- STL
1 stop28h 30m
Frontier
Mon 5/259:06 pm
STL
- ONT
1 stop12h 58m
Frontier
Deal found 4/19![Frontier logo]()
$198
This CheapOair deal was found by Cheapflights users on 4/21. 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 5/194:39 pm
ONT
- STL
1 stop23h 27m
Frontier
Wed 6/36:51 pm
STL
- ONT
1 stop22h 18m
Frontier
Deal found 4/21![Frontier logo]()
$185
This Booking.com deal was found by Cheapflights users on 4/20. 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 5/2210:50 am
ONT
- STL
1 stop6h 33m
Frontier
Tue 6/238:08 pm
STL
- ONT
1 stop5h 41m
Frontier
Deal found 4/20![Frontier logo]()
$186
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 April 22, 2026.
Search for one-way flight options from Ontario to St. Louis. Find affordable one-way fares based on user searches. Data last updated April 22, 2026.
This Super.com deal was found by Cheapflights users on 4/18. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 5/238:43 am
ONT
- STL
1 stop8h 48m
Frontier
Deal found 4/18![Frontier logo]()
$79
This Frontier deal was found by Cheapflights users on 4/20. 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 5/1111:36 am
ONT
- STL
1 stop6h 47m
Frontier
Deal found 4/20![Frontier logo]()
$80
This Super.com deal was found by Cheapflights users on 4/19. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 5/134:39 pm
ONT
- STL
1 stop17h 02m
Frontier
Deal found 4/19![Frontier logo]()
$85
This Mytrip deal was found by Cheapflights users on 4/19. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Mytrip is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 5/144:04 pm
ONT
- STL
1 stop26h 19m
Frontier
Deal found 4/19![Frontier logo]()
$86
This Super.com deal was found by Cheapflights users on 4/20. 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.
Sat 5/910:50 am
ONT
- STL
1 stop6h 33m
Frontier
Deal found 4/20![Frontier logo]()
$99
This Super.com deal was found by Cheapflights users on 4/22. 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 5/811:36 am
ONT
- STL
1 stop6h 47m
Frontier
Deal found 4/22![Frontier logo]()
$104
This Super.com deal was found by Cheapflights users on 4/17. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 5/64:39 pm
ONT
- STL
1 stop17h 02m
Frontier
Deal found 4/17![Frontier logo]()
$105
This CheapOair deal was found by Cheapflights users on 4/20. 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.
Sun 5/104:04 pm
ONT
- STL
1 stop26h 19m
Frontier
Deal found 4/20![Frontier logo]()
$106
This Super.com deal was found by Cheapflights users on 4/22. 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.
Tue 6/231:33 pm
ONT
- STL
1 stop27h 18m
Frontier
Deal found 4/22![Frontier logo]()
$110
This Frontier deal was found by Cheapflights users on 4/20. 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 6/56:00 am
ONT
- STL
1 stop11h 23m
Frontier
Deal found 4/20![Frontier logo]()
$111
This CheapOair deal was found by Cheapflights users on 4/19. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure CheapOair is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 7/81:27 pm
ONT
- STL
1 stop28h 09m
Frontier
Deal found 4/19![Frontier logo]()
$117
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 April 22, 2026.
Most accurate provider | FlightHub 3 stars |
|---|---|
Most trusted provider | FlightHub 3 stars |
Round-trip from | $160 (Frontier) |
One-way from | $79 (Super.com) |
Popular in | December |
Cheapest in | September |
Average price | $250 |
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 April 22, 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
Thu 5/28
10:50 am-7:23 pm
1 stop6h 33m
Lambert-St Louis
Sun 5/31
9:06 pm-3:09 pm
1 stop20h 03m
$213
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
Tue 9/22
7:10 am-5:03 pm
1 stop7h 53m
Lambert-St Louis
Wed 9/30
3:17 pm-11:24 pm
1 stop10h 07m
$341
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
Wed 5/13
4:39 pm-11:41 am
1 stop17h 02m
Lambert-St Louis
Sat 5/16
7:08 pm-7:32 pm
2 stops26h 24m
$382
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
Thu 5/21
11:51 am-8:11 pm
1 stop6h 20m
Lambert-St Louis
Tue 5/26
5:33 pm-11:12 am
2 stops19h 39m
$404
Quickest round-trip
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
Sun 7/19
10:50 am-7:23 pm
1 stop6h 33m
Lambert-St Louis
Wed 7/22
8:08 pm-11:49 pm
1 stop5h 41m
$420
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
Mon 5/25
10:00 pm-9:44 am
1 stop9h 44m
Lambert-St Louis
Mon 6/1
7:59 pm-11:34 pm
1 stop5h 35m
$423
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
Sun 9/13
9:01 am-6:24 pm
1 stop7h 23m
Lambert-St Louis
Thu 9/17
5:10 am-12:12 pm
2 stops9h 02m
$428
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
Fri 5/29
6:45 am-7:03 pm
2 stops10h 18m
Lambert-St Louis
Tue 6/2
7:59 pm-11:34 pm
1 stop5h 35m
$441
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
Wed 5/13
6:00 am-6:45 pm
1 stop10h 45m
Lambert-St Louis
Sat 5/16
5:33 pm-11:56 pm
1 stop8h 23m
$450
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
Wed 5/13
6:15 am-5:21 pm
2 stops9h 06m
Lambert-St Louis
Sat 5/16
12:27 pm-7:34 pm
2 stops9h 07m
$460
Showing 1-10 of 23 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 April.
| 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 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?
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 April 17, 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 $241). 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 83% 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 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 April 22, 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.
Entertainment
7.5
Overall
8.0
Crew
8.6
Food
7.0
Comfort
8.0
Boarding
8.1
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Entertainment
7.5
Overall
8.0
Crew
8.6
Food
7.0
Comfort
8.0
Boarding
8.1
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Entertainment
7.5
Overall
8.0
Crew
8.6
Food
7.0
Comfort
8.0
Boarding
8.1
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Entertainment
7.5
Overall
8.0
Crew
8.6
Food
7.0
Comfort
8.0
Boarding
8.1
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Entertainment
7.5
Overall
8.0
Crew
8.6
Food
7.0
Comfort
8.0
Boarding
8.1
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Entertainment
7.5
Overall
8.0
Crew
8.6
Food
7.0
Comfort
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 locationsEdwardsville
O'Fallon
Fenton
Swansea
Fairview Heights
Maryland Heights
Collinsville
Eureka
Wentzville
Glencoe
Chesterfield
Alton
Farmington
Festus
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Alternative routes for Ontario to St. Louis
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Complete your trip
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Ontario and St. Louis flights
Browse other Ontario and St. Louis flight options. Last updated on April 22, 2026.
Other flights from Ontario
Browse through other flights departing from Ontario. Flights are based on user searches made on Cheapflights and were last updated on April 22, 2026.
Popular flight searches
Check out other popular destinations found by fellow travelers in 2026
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 April 22, 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 April 22, 2026.
| Airline | Cheapest | Average | Flexibility | On-time |
|---|---|---|---|---|
| Cheapest$139 | Average$391 | FlexibilityNo cancel fee | On-timeN/A | |
| Cheapest$146 | Average$227 | 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$466 | FlexibilityNo cancel fee | On-time63% |