$60+ Cheap flights from Ontario (ONT) to Illinois
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 5/12. Fares are subject to change and may not be available on all flights or dates of travel.
ONT — ORD
May 21 — May 281
Round-trip
1 adult, Economy
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Find cheap flights from Ontario to Illinois with Cheapflights
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Cheapest flights from Ontario to IllinoisExplore the most affordable flight options available from Ontario to Illinois. Find the lowest fares from popular airlines and budget airlines, with prices last updated on April 21, 2026.
Explore the most affordable flight options available from Ontario to Illinois. Find the lowest fares from popular airlines and budget airlines, with prices last updated on April 21, 2026.
This Expedia deal was found by Cheapflights users on 4/16. 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 Expedia 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 4/16![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 4/16. 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.
Fri 5/88:44 am
ONT
- STL
1 stop9h 39m
Frontier
Tue 5/126:51 pm
STL
- ONT
1 stop22h 53m
Frontier
Deal found 4/16![Frontier logo]()
$171
This Booking.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 Booking.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 5/168:27 pm
ONT
- STL
1 stop13h 14m
Frontier
Tue 5/196:51 pm
STL
- ONT
1 stop22h 53m
Frontier
Deal found 4/17![Frontier logo]()
$172
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.
Fri 5/226:00 am
ONT
- STL
1 stop11h 23m
Frontier
Mon 5/259:06 pm
STL
- ONT
1 stop12h 58m
Frontier
Deal found 4/20![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 4/16. 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.
Mon 5/48:59 pm
ONT
- STL
1 stop19h 07m
Frontier
Sat 5/98:08 pm
STL
- ONT
1 stop5h 41m
Frontier
Deal found 4/16![Frontier logo]()
$187
This CheapOair deal was found by Cheapflights users on 4/16. 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.
Mon 5/412:22 pm
ONT
- STL
1 stop27h 44m
Frontier
Thu 5/78:08 pm
STL
- ONT
1 stop15h 57m
Frontier
Deal found 4/16![Frontier logo]()
$191
This Booking.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 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
Tue 5/196:51 pm
STL
- ONT
1 stop22h 53m
Frontier
Deal found 4/18![Frontier logo]()
$193
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.
Sat 5/212:59 am
ONT
- STL
1 stop16h 22m
Frontier
Sun 5/1012:36 pm
STL
- ONT
1 stop21h 13m
Frontier
Deal found 4/18![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 IllinoisDiscover carefully curated flight deals from Ontario to Illinois that have cost, travel time, and layovers in mind to ensure you get the best travel experience. Data last updated April 21, 2026.
Discover carefully curated flight deals from Ontario to Illinois that have cost, travel time, and layovers in mind to ensure you get the best travel experience. Data last updated April 21, 2026.
This Delta deal was found by Cheapflights users on 4/16. 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.
Tue 8/1810:59 pm
ONT
- MLI
1 stop9h 27m
Delta
Tue 9/2211:00 am
MLI
- ONT
1 stop9h 01m
Delta
Deal found 4/16![Delta logo]()
$331
This Kiwi.com deal was found by Cheapflights users on 4/16. 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 Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 5/98:27 pm
ONT
- RFD
1 stop13h 33m
Multiple Airlines
Sun 5/1712:50 pm
RFD
- ONT
1 stop20h 59m
Multiple Airlines
Deal found 4/16![Multiple Airlines logo]()
$368
This United Airlines 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 United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 5/161:40 pm
ONT
- PIA
1 stop5h 39m
United Airlines
Sat 5/235:33 pm
PIA
- ONT
1 stop7h 18m
United Airlines
Deal found 4/18![United Airlines logo]()
$369
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.
Tue 5/267:41 pm
ONT
- ORD
1 stop8h 39m
Alaska Airlines
Wed 6/39:00 am
ORD
- ONT
2 stops12h 08m
Alaska Airlines
Deal found 4/20![Alaska Airlines logo]()
$418
This American Airlines 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 American Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 6/207:00 am
ONT
- MLI
1 stop7h 12m
American Airlines
Sat 6/277:20 am
MLI
- ONT
1 stop6h 31m
American Airlines
Deal found 4/21![American Airlines logo]()
$459
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 Delta 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 Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 8/2912:00 pm
ONT
- MLI
1 stop8h 30m
Delta
Sun 8/305:55 am
MLI
- ONT
1 stop7h 09m
Delta
Deal found 4/19![Delta logo]()
$350
This United Airlines deal was found by Cheapflights users on 4/16. 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 United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 5/116:59 pm
ONT
- ORD
1 stop9h 21m
United Airlines
Thu 5/148:09 pm
ORD
- ONT
Nonstop4h 26m
United Airlines
Deal found 4/16![United Airlines logo]()
$394
This Expedia deal was found by Cheapflights users on 4/16. 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 Expedia is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 5/227:41 pm
ONT
- STL
2 stops18h 56m
Multiple Airlines
Mon 5/259:06 pm
STL
- ONT
1 stop20h 38m
Multiple Airlines
Deal found 4/16![Multiple Airlines logo]()
$433
This United Airlines deal was found by Cheapflights users on 4/16. 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 United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 6/171:50 pm
ONT
- ORD
1 stop9h 09m
United Airlines
Tue 6/238:13 pm
ORD
- ONT
Nonstop4h 33m
United Airlines
Deal found 4/16![United Airlines logo]()
$399
This Delta deal was found by Cheapflights users on 4/16. 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.
Wed 6/105:59 pm
ONT
- MDW
2 stops12h 38m
Delta
Mon 6/151:16 pm
MDW
- ONT
2 stops11h 25m
Delta
Deal found 4/16![Delta logo]()
$415
This Southwest deal was found by Cheapflights users on 4/16. 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 Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 6/306:10 am
ONT
- STL
2 stops8h 10m
Southwest
Tue 7/148:30 am
STL
- ONT
2 stops9h 00m
Southwest
Deal found 4/16![Southwest logo]()
$471
This Alaska Airlines deal was found by Cheapflights users on 4/16. 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.
Thu 8/2711:58 am
ONT
- STL
1 stop10h 00m
Alaska Airlines
Sat 9/123:12 pm
STL
- ONT
1 stop10h 12m
Alaska Airlines
Deal found 4/16![Alaska Airlines logo]()
$477
This American Airlines deal was found by Cheapflights users on 4/16. 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 American Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 8/512:33 pm
ONT
- PIA
1 stop8h 46m
American Airlines
Sun 8/94:24 pm
PIA
- ONT
1 stop7h 40m
American Airlines
Deal found 4/16![American Airlines logo]()
$484
This Delta deal was found by Cheapflights users on 4/16. 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 5/112:49 pm
ONT
- MLI
1 stop7h 46m
Delta
Tue 5/55:55 am
MLI
- ONT
1 stop7h 41m
Delta
Deal found 4/16![Delta logo]()
$419
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.
Sat 9/267:10 am
ONT
- STL
1 stop7h 53m
Alaska Airlines
Sat 10/37:00 am
STL
- ONT
1 stop9h 47m
Alaska Airlines
Deal found 4/17![Alaska Airlines logo]()
$477
This Southwest 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 Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 5/198:05 am
ONT
- STL
2 stops7h 50m
Southwest
Tue 5/265:30 am
STL
- ONT
2 stops8h 05m
Southwest
Deal found 4/19![Southwest logo]()
$486
This United 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 United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 5/97:00 am
ONT
- PAH
1 stop9h 19m
United Airlines
Mon 5/182:10 pm
PAH
- ONT
1 stop9h 48m
United Airlines
Deal found 4/17![United Airlines logo]()
$454
This Delta 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 Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 5/1212:08 pm
ONT
- MDW
1 stop7h 01m
Delta
Tue 5/191:22 pm
MDW
- ONT
2 stops12h 12m
Delta
Deal found 4/20![Delta logo]()
$426
This American Airlines 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 American Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 5/257:00 am
ONT
- BMI
1 stop6h 52m
American Airlines
Sat 5/305:00 am
BMI
- ONT
2 stops9h 05m
American Airlines
Deal found 4/21![American Airlines logo]()
$530
This Southwest deal was found by Cheapflights users on 4/16. 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 Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 7/216:10 am
ONT
- STL
2 stops8h 10m
Southwest
Tue 8/411:55 am
STL
- ONT
2 stops10h 10m
Southwest
Deal found 4/16![Southwest logo]()
$487
This Delta deal was found by Cheapflights users on 4/16. 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.
Mon 5/256:00 am
ONT
- MDW
2 stops9h 56m
Delta
Thu 6/41:22 pm
MDW
- ONT
2 stops12h 12m
Delta
Deal found 4/16![Delta logo]()
$427
This United Airlines deal was found by Cheapflights users on 4/16. 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 United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 8/187:13 pm
ONT
- MLI
2 stops12h 41m
United Airlines
Tue 9/222:29 pm
MLI
- ONT
2 stops8h 23m
United Airlines
Deal found 4/16![United Airlines logo]()
$485
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.
Fri 8/71:15 pm
ONT
- STL
2 stops7h 50m
Southwest
Mon 8/102:15 pm
STL
- ONT
2 stops7h 10m
Southwest
Deal found 4/20![Southwest logo]()
$487
This American 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 American Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 5/1312:19 pm
ONT
- PIA
2 stops8h 54m
American Airlines
Wed 5/205:02 am
PIA
- ONT
2 stops13h 20m
American Airlines
Deal found 4/20![American Airlines logo]()
$543
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 6/22:27 pm
STL
- ONT
2 stops10h 05m
Delta
Deal found 4/18![Delta logo]()
$435
This Southwest 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 Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 6/106:10 am
ONT
- STL
2 stops8h 10m
Southwest
Mon 6/155:35 am
STL
- ONT
2 stops7h 45m
Southwest
Deal found 4/21![Southwest logo]()
$487
This American 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 American Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 5/510:59 am
ONT
- SPI
2 stops10h 39m
American Airlines
Sat 5/95:45 am
SPI
- ONT
2 stops9h 33m
American Airlines
Deal found 4/20![American Airlines logo]()
$559
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.
Wed 5/61:40 pm
ONT
- PIA
1 stop5h 39m
United Airlines
Sun 5/105:30 pm
PIA
- ONT
1 stop7h 05m
United Airlines
Deal found 4/20![United Airlines logo]()
$519
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.
Sat 5/96:20 am
ONT
- MDW
2 stops8h 55m
Southwest
Tue 5/1211:00 am
MDW
- ONT
Nonstop4h 15m
Southwest
Deal found 4/20![Southwest logo]()
$489
Last-minute flights from Ontario to IllinoisDiscover last-minute flight deals from Ontario to Illinois. Data last updated April 21, 2026 and is based on user searches.
Discover last-minute flight deals from Ontario to Illinois. Data last updated April 21, 2026 and is based on user searches.
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.
Sat 5/212:59 am
ONT
- STL
1 stop16h 22m
Frontier
Sun 5/1012:36 pm
STL
- ONT
1 stop21h 13m
Frontier
Deal found 4/18![Frontier logo]()
$196
This Booking.com deal was found by Cheapflights users on 4/16. 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.
Mon 5/48:59 pm
ONT
- STL
1 stop19h 07m
Frontier
Sat 5/98:08 pm
STL
- ONT
1 stop5h 41m
Frontier
Deal found 4/16![Frontier logo]()
$187
This CheapOair deal was found by Cheapflights users on 4/16. 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.
Mon 5/412:22 pm
ONT
- STL
1 stop27h 44m
Frontier
Thu 5/78:08 pm
STL
- ONT
1 stop15h 57m
Frontier
Deal found 4/16![Frontier logo]()
$191
This Booking.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 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
Tue 5/196:51 pm
STL
- ONT
1 stop22h 53m
Frontier
Deal found 4/18![Frontier logo]()
$193
This Expedia deal was found by Cheapflights users on 4/16. 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 Expedia 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 4/16![Frontier logo]()
$160
This CheapOair deal was found by Cheapflights users on 4/16. 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.
Fri 5/88:44 am
ONT
- STL
1 stop9h 39m
Frontier
Tue 5/126:51 pm
STL
- ONT
1 stop22h 53m
Frontier
Deal found 4/16![Frontier logo]()
$171
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 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 Booking.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 Booking.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 5/168:27 pm
ONT
- STL
1 stop13h 14m
Frontier
Tue 5/196:51 pm
STL
- ONT
1 stop22h 53m
Frontier
Deal found 4/17![Frontier logo]()
$172
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 4/20. 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.
Fri 5/226:00 am
ONT
- STL
1 stop11h 23m
Frontier
Mon 5/259:06 pm
STL
- ONT
1 stop12h 58m
Frontier
Deal found 4/20![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 IllinoisSearch for one-way flight options from Ontario to Illinois. Find affordable one-way fares based on user searches. Data last updated April 21, 2026.
Search for one-way flight options from Ontario to Illinois. Find affordable one-way fares based on user searches. Data last updated April 21, 2026.
This Trip.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 Trip.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 5/1210:50 am
ONT
- ORD
1 stop7h 42m
Frontier
Deal found 4/18![Frontier logo]()
$60
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.
Tue 5/196:00 am
ONT
- ORD
1 stop12h 32m
Frontier
Deal found 4/17![Frontier logo]()
$77
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 4/17. 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.
Mon 5/118:06 pm
ONT
- ORD
1 stop24h 55m
Frontier
Deal found 4/17![Frontier logo]()
$85
This Booking.com deal was found by Cheapflights users on 4/16. 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.
Tue 5/124:39 pm
ONT
- STL
1 stop23h 27m
Frontier
Deal found 4/16![Frontier logo]()
$86
This CheapOair 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 CheapOair is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 5/88:06 pm
ONT
- ORD
1 stop24h 55m
Frontier
Deal found 4/17![Frontier logo]()
$86
This Jetabroad 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 Jetabroad is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 5/188:06 pm
ONT
- ORD
1 stop24h 55m
Frontier
Deal found 4/21![Frontier logo]()
$89
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 4/19. 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.
Sat 5/212:59 am
ONT
- ORD
1 stop6h 46m
Frontier
Deal found 4/19![Frontier logo]()
$99
This Booking.com deal was found by Cheapflights users on 4/16. 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.
Thu 4/3011:47 am
ONT
- STL
1 stop7h 13m
Frontier
Deal found 4/16![Frontier logo]()
$100
This Southwest deal was found by Cheapflights users on 4/16. 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 Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 6/1611:55 pm
ONT
- MDW
Nonstop3h 45m
Southwest
Deal found 4/16![Southwest logo]()
$100
Find flight deals from Ontario to Illinois
Keep the following information in mind while searching for Ontario to Illinois flight deals. Data was last updated April 21, 2026.
Most accurate provider | FlightHub 3 stars |
|---|---|
Most trusted provider | FlightHub 3 stars |
Round-trip from | $160 (Expedia) |
One-way from | $60 (Trip.com) |
Popular in | February |
Cheapest in | September |
Average price | $320 |
Good round-trip deal | $393 or less |
Good one-way deal | $210 or less |
Cheapflights Fare Finder
Customize your flight search to find flights from Ontario to Illinois 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 21, 2026.
Use the filters below to find and compare flights from Ontario to Illinois that are best for you.
Fly from
Fly to
Route
Depart
Return
Cheapest round-trip
OntarioMoline
ONT - MLI
ONTMLI
Ontario
Tue 8/18
10:59 pm-10:26 am
1 stop9h 27m
Moline Quad-City
Tue 9/22
11:00 am-6:01 pm
1 stop9h 01m
$331
OntarioMoline
ONT - MLI
ONTMLI
Ontario
Sat 8/29
12:00 pm-10:30 pm
1 stop8h 30m
Moline Quad-City
Sun 8/30
5:55 am-11:04 am
1 stop7h 09m
$350
OntarioChicago
ONT - RFD
ONTRFD
Ontario
Sat 5/9
8:27 pm-12:00 pm
1 stop13h 33m
Chicago Greater Rockford
Sun 5/17
12:50 pm-7:49 am
1 stop20h 59m
$368
OntarioPeoria
ONT - PIA
ONTPIA
Ontario
Sat 5/16
1:40 pm-9:19 pm
1 stop5h 39m
Greater Peoria
Sat 5/23
5:33 pm-10:51 pm
1 stop7h 18m
$369
OntarioChicago
ONT - ORD
ONTORD
Ontario
Mon 5/11
6:59 pm-6:20 am
1 stop9h 21m
Chicago O'Hare Intl
Thu 5/14
8:09 pm-10:35 pm
Nonstop4h 26m
$394
OntarioChicago
ONT - ORD
ONTORD
Ontario
Wed 6/17
1:50 pm-12:59 am
1 stop9h 09m
Chicago O'Hare Intl
Tue 6/23
8:13 pm-10:46 pm
Nonstop4h 33m
$399
OntarioChicago
ONT - MDW
ONTMDW
Ontario
Wed 6/10
5:59 pm-8:37 am
2 stops12h 38m
Chicago Midway
Mon 6/15
1:16 pm-10:41 pm
2 stops11h 25m
$415
OntarioChicago
ONT - ORD
ONTORD
Ontario
Tue 5/26
7:41 pm-6:20 am
1 stop8h 39m
Chicago O'Hare Intl
Wed 6/3
9:00 am-7:08 pm
2 stops12h 08m
$418
OntarioMoline
ONT - MLI
ONTMLI
Ontario
Fri 5/1
12:49 pm-10:35 pm
1 stop7h 46m
Moline Quad-City
Tue 5/5
5:55 am-11:36 am
1 stop7h 41m
$419
OntarioChicago
ONT - MDW
ONTMDW
Ontario
Tue 5/12
12:08 pm-9:09 pm
1 stop7h 01m
Chicago Midway
Tue 5/19
1:22 pm-11:34 pm
2 stops12h 12m
$426
Showing 1-10 of 60 resultsSorted by cheapest first
Best time to book a flight from Ontario to Illinois
Have a flexible travel schedule? Discover the best time to fly to Illinois from Ontario with our price prediction graph.
ONT-STL
ONT-MDW
ONT-RFD
ONT-ORD
ONT-SPI
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 Illinois
ONT-USIL
ONT-STL
ONT-MDW
ONT-RFD
ONT-ORD
What is the cheapest month to book a flight from Ontario to Illinois?
Currently, April is the cheapest month in which you can book a flight from Ontario to Illinois (average of $88). Flying from Ontario to Illinois in March is currently the most expensive (average of $186). There are several factors that can impact the price of a flight, so comparing airlines, departure airports and flight times can provide users with more options.
What is the cheapest time of day to fly from ONT to IL?
Find hourly flight availability from Ontario to Illinois. Discover flight options and departure times throughout the day, allowing you to choose a departure time that suits your schedule. Data last updated April 21, 2026.
Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Ontario to Illinois as you normally would.
How much does it cost to fly round-trip from Ontario to Illinois?
Reviews of airlines servicing Illinois
Get insights into the airlines that provide service to Illinois. 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 Illinois. Reviews last updated April 21, 2026.
Read through reviews of airlines operating flights from Ontario to Illinois, such as Southwest,Delta, andUnited Airlines. You can also see how each airline stacks up in terms of entertainment options, comfort, food, crew/service, and boarding process.
Food
7.0
Crew
8.6
Overall
8.0
Comfort
8.0
Boarding
8.1
Entertainment
7.5
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Food
7.0
Crew
8.6
Overall
8.0
Comfort
8.0
Boarding
8.1
Entertainment
7.5
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Food
7.0
Crew
8.6
Overall
8.0
Comfort
8.0
Boarding
8.1
Entertainment
7.5
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Food
7.0
Crew
8.6
Overall
8.0
Comfort
8.0
Boarding
8.1
Entertainment
7.5
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Food
7.0
Crew
8.6
Overall
8.0
Comfort
8.0
Boarding
8.1
Entertainment
7.5
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Food
7.0
Crew
8.6
Overall
8.0
Comfort
8.0
Boarding
8.1
Entertainment
7.5
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 Illinois. Access travel guides, tips, and recommendations to enhance your travel experience. Get information about local attractions, weather, transportation options, and more.
Browse thousands of different options on Cheapflights for your next trip
Toggle through the tabs below to find thousands of options on Cheapflights for your next trip.
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Alternative routes for Ontario to Illinois
See prices for flight routes from nearby airports that may be better suited for you.
Complete your trip
Complete your trip to Illinois by adding a car rental and/or hotel reservation to your travel itinerary.
Search flights from Ontario to Illinois by cabin class
Find flights from Ontario to Illinois, based on your preferred cabin class, be it economy, premium economy, business, or first class.
Ontario and Illinois flights
Browse other Ontario and Illinois flight options. Last updated on April 21, 2026.
Popular flight searches
Check out other popular destinations found by fellow travelers in 2026
Ontario to Illinois flights
Consider these flights traveling from Ontario to Illinois.
Top 5 airlines flying from Ontario to Illinois
Discover the top 5 airlines that operate flights from Ontario to Illinois. 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 21, 2026.
| Airline | Cheapest | Average | Flexibility | On-time |
|---|---|---|---|---|
| Cheapest$117 | Average$241 | FlexibilityNo cancel fee | On-time62% | |
| Cheapest$226 | Average$468 | FlexibilityNo cancel fee | On-time69% | |
| Cheapest$237 | Average$380 | FlexibilityNo cancel fee | On-time63% | |
| Cheapest$260 | Average$442 | FlexibilityNo cancel fee | On-timeN/A | |
| Cheapest$288 | Average$528 | FlexibilityNo cancel fee | On-time71% |