$80+ 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 5/16. Fares are subject to change and may not be available on all flights or dates of travel.
ONT — STL
Apr 20 — Apr 271
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 March 21, 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 March 21, 2026.
This Gotogate deal was found by Cheapflights users on 3/20. 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 Gotogate is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 4/175:33 pm
ONT
- STL
1 stop23h 59m
Frontier
Sun 4/199:55 pm
STL
- ONT
1 stop14h 19m
Frontier
Deal found 3/20![Frontier logo]()
$160
This CheapOair deal was found by Cheapflights users on 3/20. 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.
Wed 4/1512:59 am
ONT
- STL
1 stop16h 22m
Frontier
Sun 4/199:55 pm
STL
- ONT
1 stop14h 19m
Frontier
Deal found 3/20![Frontier logo]()
$171
This Booking.com deal was found by Cheapflights users on 3/20. 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.
Sat 5/169:15 am
ONT
- STL
1 stop6h 49m
Frontier
Sat 5/238:08 pm
STL
- ONT
1 stop5h 41m
Frontier
Deal found 3/20![Frontier logo]()
$186
This Booking.com deal was found by Cheapflights users on 3/20. 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.
Mon 5/412:22 pm
ONT
- STL
1 stop27h 44m
Frontier
Sun 5/1012:16 pm
STL
- ONT
1 stop21h 33m
Frontier
Deal found 3/20![Frontier logo]()
$187
This CheapOair deal was found by Cheapflights users on 3/20. 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.
Wed 4/157:44 pm
ONT
- STL
1 stop23h 16m
Frontier
Sun 4/199:55 pm
STL
- ONT
1 stop14h 19m
Frontier
Deal found 3/20![Frontier logo]()
$196
This Frontier deal was found by Cheapflights users on 3/19. 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 Frontier 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
Mon 4/203:21 pm
STL
- ONT
1 stop10h 22m
Frontier
Deal found 3/19![Frontier logo]()
$205
This Frontier deal was found by Cheapflights users on 3/19. 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 Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 4/1712:59 am
ONT
- STL
1 stop16h 33m
Frontier
Fri 4/249:58 pm
STL
- ONT
1 stop22h 51m
Frontier
Deal found 3/19![Frontier logo]()
$211
This Frontier deal was found by Cheapflights users on 3/17. 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 4/1712:59 am
ONT
- STL
1 stop16h 33m
Frontier
Sat 4/258:17 pm
STL
- ONT
1 stop13h 09m
Frontier
Deal found 3/17![Frontier logo]()
$213
This Frontier deal was found by Cheapflights users on 3/20. 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.
Sun 4/510:35 pm
ONT
- STL
1 stop10h 47m
Frontier
Wed 4/88:16 pm
STL
- ONT
1 stop5h 40m
Frontier
Deal found 3/20![Frontier logo]()
$215
This Mytrip deal was found by Cheapflights users on 3/16. 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 4/76:20 am
ONT
- STL
1 stop25h 28m
Frontier
Wed 4/88:16 pm
STL
- ONT
1 stop5h 40m
Frontier
Deal found 3/16![Frontier logo]()
$216
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 March 21, 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 March 21, 2026.
This Booking.com deal was found by Cheapflights users on 3/20. 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.
Sat 5/169:15 am
ONT
- STL
1 stop6h 49m
Frontier
Sat 5/238:08 pm
STL
- ONT
1 stop5h 41m
Frontier
Deal found 3/20![Frontier logo]()
$186
This Delta deal was found by Cheapflights users on 3/17. 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 Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 4/76:00 am
ONT
- STL
1 stop5h 17m
Delta
Tue 4/76:12 pm
STL
- ONT
1 stop7h 39m
Delta
Deal found 3/17![Delta logo]()
$333
This CheapOair deal was found by Cheapflights users on 3/16. 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 5/61:50 pm
ONT
- STL
1 stop19h 31m
Frontier
Sat 5/98:08 pm
STL
- ONT
1 stop15h 57m
Frontier
Deal found 3/16![Frontier logo]()
$210
This Alaska Airlines deal was found by Cheapflights users on 3/16. 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.
Fri 4/177:08 pm
ONT
- STL
1 stop26h 51m
Alaska Airlines
Tue 4/213:50 pm
STL
- ONT
1 stop10h 09m
Alaska Airlines
Deal found 3/16![Alaska Airlines logo]()
$455
This Delta deal was found by Cheapflights users on 3/20. 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 Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 4/181:29 pm
ONT
- STL
1 stop6h 02m
Delta
Wed 4/226:45 pm
STL
- ONT
1 stop6h 59m
Delta
Deal found 3/20![Delta logo]()
$333
This Delta deal was found by Cheapflights users on 3/16. 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.
Thu 4/236:00 am
ONT
- STL
1 stop5h 23m
Delta
Wed 4/296:45 pm
STL
- ONT
1 stop6h 59m
Delta
Deal found 3/16![Delta logo]()
$343
This Delta deal was found by Cheapflights users on 3/20. 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 Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 4/225:05 pm
ONT
- STL
1 stop5h 20m
Delta
Sat 4/255:00 pm
STL
- ONT
1 stop7h 43m
Delta
Deal found 3/20![Delta logo]()
$360
This Kiwi.com deal was found by Cheapflights users on 3/20. 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 Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 4/73:21 pm
ONT
- STL
2 stops16h 27m
Frontier
Mon 4/1312:22 pm
STL
- ONT
1 stop24h 22m
Frontier
Deal found 3/20![Frontier logo]()
$409
This Delta deal was found by Cheapflights users on 3/17. 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 Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 5/84:57 pm
ONT
- STL
1 stop5h 33m
Delta
Tue 5/127:00 am
STL
- ONT
1 stop7h 19m
Delta
Deal found 3/17![Delta logo]()
$417
This Delta deal was found by Cheapflights users on 3/17. 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 Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 4/205:05 pm
ONT
- STL
1 stop5h 20m
Delta
Sat 4/256:00 am
STL
- ONT
1 stop7h 36m
Delta
Deal found 3/17![Delta logo]()
$423
This Delta deal was found by Cheapflights users on 3/16. 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 4/310:25 pm
ONT
- STL
1 stop8h 37m
Delta
Wed 4/87:15 am
STL
- ONT
1 stop7h 08m
Delta
Deal found 3/16![Delta logo]()
$467
This Delta deal was found by Cheapflights users on 3/16. 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.
Thu 4/25:09 pm
ONT
- STL
1 stop5h 12m
Delta
Tue 4/76:12 pm
STL
- ONT
1 stop7h 39m
Delta
Deal found 3/16![Delta logo]()
$467
Last-minute flights from Ontario to St. LouisDiscover last-minute flight deals from Ontario to St. Louis. Data last updated March 21, 2026 and is based on user searches.
Discover last-minute flight deals from Ontario to St. Louis. Data last updated March 21, 2026 and is based on user searches.
This Frontier deal was found by Cheapflights users on 3/20. 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.
Sun 4/510:35 pm
ONT
- STL
1 stop10h 47m
Frontier
Wed 4/88:16 pm
STL
- ONT
1 stop5h 40m
Frontier
Deal found 3/20![Frontier logo]()
$215
This Frontier deal was found by Cheapflights users on 3/20. 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.
Sun 4/510:35 pm
ONT
- STL
1 stop10h 47m
Frontier
Thu 4/91:14 pm
STL
- ONT
1 stop6h 01m
Frontier
Deal found 3/20![Frontier logo]()
$220
This Mytrip deal was found by Cheapflights users on 3/16. 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 4/76:20 am
ONT
- STL
1 stop25h 28m
Frontier
Wed 4/88:16 pm
STL
- ONT
1 stop5h 40m
Frontier
Deal found 3/16![Frontier logo]()
$216
This Booking.com deal was found by Cheapflights users on 3/20. 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 4/106:20 am
ONT
- STL
1 stop25h 28m
Frontier
Fri 4/178:06 pm
STL
- ONT
1 stop5h 49m
Frontier
Deal found 3/20![Frontier logo]()
$217
This CheapOair deal was found by Cheapflights users on 3/20. 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.
Wed 4/1512:59 am
ONT
- STL
1 stop16h 22m
Frontier
Sun 4/199:55 pm
STL
- ONT
1 stop14h 19m
Frontier
Deal found 3/20![Frontier logo]()
$171
This CheapOair deal was found by Cheapflights users on 3/20. 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.
Wed 4/157:44 pm
ONT
- STL
1 stop23h 16m
Frontier
Sun 4/199:55 pm
STL
- ONT
1 stop14h 19m
Frontier
Deal found 3/20![Frontier logo]()
$196
This Frontier deal was found by Cheapflights users on 3/19. 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 Frontier 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
Mon 4/203:21 pm
STL
- ONT
1 stop10h 22m
Frontier
Deal found 3/19![Frontier logo]()
$205
This Gotogate deal was found by Cheapflights users on 3/20. 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 Gotogate is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 4/175:33 pm
ONT
- STL
1 stop23h 59m
Frontier
Sun 4/199:55 pm
STL
- ONT
1 stop14h 19m
Frontier
Deal found 3/20![Frontier logo]()
$160
This Frontier deal was found by Cheapflights users on 3/19. 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 Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 4/1712:59 am
ONT
- STL
1 stop16h 33m
Frontier
Fri 4/249:58 pm
STL
- ONT
1 stop22h 51m
Frontier
Deal found 3/19![Frontier logo]()
$211
This Frontier deal was found by Cheapflights users on 3/17. 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 4/1712:59 am
ONT
- STL
1 stop16h 33m
Frontier
Sat 4/258:17 pm
STL
- ONT
1 stop13h 09m
Frontier
Deal found 3/17![Frontier logo]()
$213
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 March 21, 2026.
Search for one-way flight options from Ontario to St. Louis. Find affordable one-way fares based on user searches. Data last updated March 21, 2026.
This Priceline deal was found by Cheapflights users on 3/20. 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 Priceline is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 5/169:15 am
ONT
- STL
1 stop6h 49m
Frontier
Deal found 3/20![Frontier logo]()
$80
This Trip.com deal was found by Cheapflights users on 3/17. 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.
Fri 4/106:20 am
ONT
- STL
1 stop25h 28m
Frontier
Deal found 3/17![Frontier logo]()
$99
This CheapOair deal was found by Cheapflights users on 3/17. 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 CheapOair 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
Deal found 3/17![Frontier logo]()
$105
This Super.com deal was found by Cheapflights users on 3/18. 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.
Thu 4/3012:59 am
ONT
- STL
1 stop16h 22m
Frontier
Deal found 3/18![Frontier logo]()
$109
This Super.com deal was found by Cheapflights users on 3/19. 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.
Tue 5/51:50 pm
ONT
- STL
1 stop26h 16m
Frontier
Deal found 3/19![Frontier logo]()
$110
This Booking.com deal was found by Cheapflights users on 3/16. 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 4/110:03 pm
ONT
- STL
1 stop21h 14m
Frontier
Deal found 3/16![Frontier logo]()
$111
This Booking.com deal was found by Cheapflights users on 3/17. 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 Booking.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 4/305:43 pm
ONT
- STL
1 stop23h 38m
Frontier
Deal found 3/17![Frontier logo]()
$112
This Gotogate deal was found by Cheapflights users on 3/16. 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 Gotogate is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 3/316:15 am
ONT
- STL
1 stop25h 33m
Frontier
Deal found 3/16![Frontier logo]()
$116
This Super.com deal was found by Cheapflights users on 3/19. 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.
Mon 4/206:15 am
ONT
- STL
1 stop6h 21m
Frontier
Deal found 3/19![Frontier logo]()
$124
This CheapOair deal was found by Cheapflights users on 3/16. 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 6/410:50 am
ONT
- STL
1 stop6h 33m
Frontier
Deal found 3/16![Frontier logo]()
$125
This Super.com deal was found by Cheapflights users on 3/18. 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 5/236:00 am
ONT
- STL
1 stop11h 23m
Frontier
Deal found 3/18![Frontier logo]()
$129
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 March 21, 2026.
Most accurate provider | FlightHub 3 stars |
|---|---|
Most trusted provider | FlightHub 3 stars |
Round-trip from | $160 (Gotogate) |
One-way from | $80 (Priceline) |
Popular in | December |
Cheapest in | September |
Average price | $360 |
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 March 21, 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
Sat 5/16
9:15 am-6:04 pm
1 stop6h 49m
Lambert-St Louis
Sat 5/23
8:08 pm-11:49 pm
1 stop5h 41m
$186
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
Wed 5/6
1:50 pm-11:21 am
1 stop19h 31m
Lambert-St Louis
Sat 5/9
8:08 pm-10:05 am
1 stop15h 57m
$210
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
Tue 4/7
6:00 am-1:17 pm
1 stop5h 17m
Lambert-St Louis
Tue 4/7
6:12 pm-11:51 pm
1 stop7h 39m
$333
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
Sat 4/18
1:29 pm-9:31 pm
1 stop6h 02m
Lambert-St Louis
Wed 4/22
6:45 pm-11:44 pm
1 stop6h 59m
$333
Quickest round-trip
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
Thu 4/23
6:00 am-1:23 pm
1 stop5h 23m
Lambert-St Louis
Wed 4/29
6:45 pm-11:44 pm
1 stop6h 59m
$343
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
Wed 4/22
5:05 pm-12:25 am
1 stop5h 20m
Lambert-St Louis
Sat 4/25
5:00 pm-10:43 pm
1 stop7h 43m
$360
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
Tue 4/7
3:21 pm-9:48 am
2 stops16h 27m
Lambert-St Louis
Mon 4/13
12:22 pm-10:44 am
1 stop24h 22m
$409
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
Fri 5/8
4:57 pm-12:30 am
1 stop5h 33m
Lambert-St Louis
Tue 5/12
7:00 am-12:19 pm
1 stop7h 19m
$417
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
Mon 4/20
5:05 pm-12:25 am
1 stop5h 20m
Lambert-St Louis
Sat 4/25
6:00 am-11:36 am
1 stop7h 36m
$423
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
Fri 4/17
7:08 pm-11:59 pm
1 stop26h 51m
Lambert-St Louis
Tue 4/21
3:50 pm-11:59 pm
1 stop10h 09m
$455
Showing 1-10 of 24 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 March.
| 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 March 13, 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 February is currently the most expensive (average of $284). 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 March 21, 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
Food
7.0
Comfort
8.0
Boarding
8.1
Overall
8.0
Crew
8.6
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Entertainment
7.5
Food
7.0
Comfort
8.0
Boarding
8.1
Overall
8.0
Crew
8.6
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Entertainment
7.5
Food
7.0
Comfort
8.0
Boarding
8.1
Overall
8.0
Crew
8.6
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Entertainment
7.5
Food
7.0
Comfort
8.0
Boarding
8.1
Overall
8.0
Crew
8.6
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Entertainment
7.5
Food
7.0
Comfort
8.0
Boarding
8.1
Overall
8.0
Crew
8.6
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Entertainment
7.5
Food
7.0
Comfort
8.0
Boarding
8.1
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
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 March 21, 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 March 21, 2026.
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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 March 21, 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 March 21, 2026.
| Airline | Cheapest | Average | Flexibility | On-time |
|---|---|---|---|---|
| Cheapest$139 | Average$391 | FlexibilityNo cancel fee | On-timeN/A | |
| Cheapest$146 | Average$230 | FlexibilityNo cancel fee | On-time62% | |
| Cheapest$292 | Average$506 | FlexibilityNo cancel fee | On-time69% | |
| Cheapest$292 | Average$396 | FlexibilityNo cancel fee | On-time71% | |
| Cheapest$338 | Average$427 | FlexibilityNo cancel fee | On-time63% |