$80+ 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 8/12. Fares are subject to change and may not be available on all flights or dates of travel.
ONT — ORD
Jun 14 — Jun 211
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 May 15, 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 May 15, 2026.
This Trip.com deal was found by Cheapflights users on 5/12. 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 8/2510:50 am
ONT
- STL
1 stop6h 33m
Frontier
Tue 9/18:08 pm
STL
- ONT
1 stop5h 41m
Frontier
Deal found 5/12![Frontier logo]()
$185
This Kiwi.com deal was found by Cheapflights users on 5/14. 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 8/126:00 am
ONT
- STL
1 stop11h 23m
Frontier
Wed 8/268:08 pm
STL
- ONT
1 stop15h 57m
Frontier
Deal found 5/14![Frontier logo]()
$197
This Kiwi.com deal was found by Cheapflights users on 5/14. 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 8/1210:49 am
ONT
- STL
1 stop6h 34m
Frontier
Mon 8/315:33 pm
STL
- ONT
2 stops32h 16m
Frontier
Deal found 5/14![Frontier logo]()
$200
This Expedia deal was found by Cheapflights users on 5/12. 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.
Tue 6/93:34 pm
ONT
- STL
1 stop24h 34m
Frontier
Tue 6/238:08 pm
STL
- ONT
1 stop5h 41m
Frontier
Deal found 5/12![Frontier logo]()
$210
This Kiwi.com deal was found by Cheapflights users on 5/14. 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 8/1210:49 am
ONT
- STL
1 stop6h 34m
Frontier
Fri 8/285:33 pm
STL
- ONT
2 stops26h 19m
Frontier
Deal found 5/14![Frontier logo]()
$216
This Super.com deal was found by Cheapflights users on 5/12. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 7/223:40 pm
ONT
- STL
1 stop20h 27m
Frontier
Tue 7/287:03 pm
STL
- ONT
1 stop26h 50m
Frontier
Deal found 5/12![Frontier logo]()
$219
This CheapOair deal was found by Cheapflights users on 5/11. 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 7/151:28 pm
ONT
- STL
1 stop22h 39m
Frontier
Tue 7/217:03 pm
STL
- ONT
1 stop26h 50m
Frontier
Deal found 5/11![Frontier logo]()
$220
This CheapOair deal was found by Cheapflights users on 5/13. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure CheapOair is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 6/34:39 pm
ONT
- STL
1 stop25h 32m
Frontier
Sat 6/68:08 pm
STL
- ONT
1 stop15h 57m
Frontier
Deal found 5/13![Frontier logo]()
$224
This Trip.com deal was found by Cheapflights users on 5/12. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Trip.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 6/101:33 pm
ONT
- STL
1 stop22h 33m
Frontier
Wed 6/177:46 pm
STL
- ONT
1 stop21h 22m
Frontier
Deal found 5/12![Frontier logo]()
$226
This Frontier deal was found by Cheapflights users on 5/11. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 6/26:00 am
ONT
- STL
1 stop11h 23m
Frontier
Wed 6/38:08 pm
STL
- ONT
1 stop5h 41m
Frontier
Deal found 5/11![Frontier logo]()
$230
This Booking.com deal was found by Cheapflights users on 5/10. 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 6/101:33 pm
ONT
- STL
1 stop22h 33m
Frontier
Mon 6/152:56 pm
STL
- ONT
1 stop6h 55m
Frontier
Deal found 5/10![Frontier logo]()
$232
This Frontier deal was found by Cheapflights users on 5/12. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 5/266:00 am
ONT
- STL
1 stop11h 23m
Frontier
Sat 6/68:08 pm
STL
- ONT
1 stop5h 41m
Frontier
Deal found 5/12![Frontier logo]()
$234
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 May 15, 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 May 15, 2026.
This deal was found by Cheapflights users on 5/14. 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 is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 9/178:07 am
ONT
- STL
1 stop7h 37m
Frontier
Mon 9/218:10 pm
STL
- ONT
1 stop5h 45m
Frontier
Deal found 5/14![Frontier logo]()
$216
This Alaska Airlines deal was found by Cheapflights users on 5/15. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Alaska Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 10/266:54 pm
ONT
- ORD
1 stop9h 26m
Alaska Airlines
Wed 10/289:00 am
ORD
- ONT
1 stop11h 00m
Alaska Airlines
Deal found 5/15![Alaska Airlines logo]()
$307
This Delta deal was found by Cheapflights users on 5/10. 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 7/810:00 pm
ONT
- MDW
2 stops12h 38m
Delta
Wed 7/151:18 pm
MDW
- ONT
2 stops12h 30m
Delta
Deal found 5/10![Delta logo]()
$308
This Southwest deal was found by Cheapflights users on 5/10. 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 7/85:30 am
ONT
- MDW
1 stop5h 55m
Southwest
Wed 7/1510:10 am
MDW
- ONT
2 stops7h 20m
Southwest
Deal found 5/10![Southwest logo]()
$329
This United Airlines deal was found by Cheapflights users on 5/10. 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 7/186:10 am
ONT
- ORD
Nonstop4h 15m
United Airlines
Wed 7/228:18 pm
ORD
- ONT
Nonstop4h 33m
United Airlines
Deal found 5/10![United Airlines logo]()
$348
This American Airlines deal was found by Cheapflights users on 5/15. 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 5/305:44 am
ONT
- PIA
1 stop8h 13m
American Airlines
Tue 6/24:20 pm
PIA
- ONT
1 stop8h 16m
American Airlines
Deal found 5/15![American Airlines logo]()
$464
This Kiwi.com deal was found by Cheapflights users on 5/12. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 7/228:39 pm
ONT
- RFD
2 stops13h 45m
Multiple Airlines
Sun 7/261:14 pm
RFD
- ONT
1 stop8h 39m
Multiple Airlines
Deal found 5/12![Multiple Airlines logo]()
$466
This Southwest deal was found by Cheapflights users on 5/14. 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 8/111:55 pm
ONT
- MDW
Nonstop3h 45m
Southwest
Tue 8/45:15 pm
MDW
- ONT
1 stop6h 50m
Southwest
Deal found 5/14![Southwest logo]()
$358
This Delta deal was found by Cheapflights users on 5/11. 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 10/1412:00 pm
ONT
- BMI
1 stop8h 23m
Delta
Tue 10/204:00 pm
BMI
- ONT
1 stop8h 14m
Delta
Deal found 5/11![Delta logo]()
$359
This United Airlines deal was found by Cheapflights users on 5/12. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 8/201:18 pm
ONT
- ORD
1 stop7h 28m
United Airlines
Tue 8/257:00 am
ORD
- ONT
1 stop7h 50m
United Airlines
Deal found 5/12![United Airlines logo]()
$393
This Delta deal was found by Cheapflights users on 5/11. 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 10/1612:00 pm
ONT
- BMI
1 stop8h 23m
Delta
Mon 10/194:00 pm
BMI
- ONT
1 stop8h 14m
Delta
Deal found 5/11![Delta logo]()
$359
This United Airlines deal was found by Cheapflights users on 5/11. 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 8/189:15 am
ONT
- ORD
1 stop7h 15m
United Airlines
Wed 8/195:30 pm
ORD
- ONT
Nonstop4h 27m
United Airlines
Deal found 5/11![United Airlines logo]()
$414
This Southwest deal was found by Cheapflights users on 5/11. 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.
Mon 6/89:40 pm
ONT
- MDW
1 stop5h 45m
Southwest
Mon 6/155:15 am
MDW
- ONT
2 stops8h 05m
Southwest
Deal found 5/11![Southwest logo]()
$417
This Delta deal was found by Cheapflights users on 5/11. 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 5/2712:07 pm
ONT
- MLI
1 stop8h 14m
Delta
Sat 5/305:56 am
MLI
- ONT
2 stops12h 21m
Delta
Deal found 5/11![Delta logo]()
$380
This Kiwi.com deal was found by Cheapflights users on 5/12. 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 7/48:36 pm
ONT
- RFD
2 stops13h 48m
Multiple Airlines
Sun 7/121:14 pm
RFD
- ONT
1 stop27h 53m
Multiple Airlines
Deal found 5/12![Multiple Airlines logo]()
$474
This American Airlines deal was found by Cheapflights users on 5/14. 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 8/97:12 am
PIA
- ONT
1 stop6h 30m
American Airlines
Deal found 5/14![American Airlines logo]()
$494
This United Airlines deal was found by Cheapflights users on 5/10. 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 7/226:10 am
ONT
- ORD
Nonstop4h 15m
United Airlines
Tue 7/286:00 am
ORD
- ONT
1 stop8h 47m
United Airlines
Deal found 5/10![United Airlines logo]()
$414
This Alaska Airlines deal was found by Cheapflights users on 5/10. 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 9/47:57 pm
ONT
- ORD
1 stop8h 25m
Alaska Airlines
Sun 9/62:22 pm
ORD
- ONT
1 stop8h 02m
Alaska Airlines
Deal found 5/10![Alaska Airlines logo]()
$505
This Southwest deal was found by Cheapflights users on 5/13. 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.
Mon 6/155:15 pm
ONT
- MDW
1 stop5h 20m
Southwest
Wed 6/247:00 am
MDW
- ONT
2 stops7h 55m
Southwest
Deal found 5/13![Southwest logo]()
$418
This Kiwi.com deal was found by Cheapflights users on 5/12. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 6/43:30 pm
ONT
- RFD
2 stops26h 50m
Multiple Airlines
Sun 6/71:13 pm
RFD
- ONT
1 stop8h 19m
Multiple Airlines
Deal found 5/12![Multiple Airlines logo]()
$494
This Southwest deal was found by Cheapflights users on 5/13. 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 6/68:40 pm
ONT
- MDW
1 stop7h 20m
Southwest
Mon 6/85:15 am
MDW
- ONT
1 stop5h 50m
Southwest
Deal found 5/13![Southwest logo]()
$427
This Delta deal was found by Cheapflights users on 5/11. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 7/2110:00 pm
ONT
- ORD
2 stops13h 03m
Delta
Mon 8/37:44 pm
ORD
- ONT
1 stop5h 50m
Delta
Deal found 5/11![Delta logo]()
$443
This United Airlines deal was found by Cheapflights users on 5/12. 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 7/226:10 am
ONT
- ORD
Nonstop4h 15m
United Airlines
Sun 7/268:18 pm
ORD
- ONT
Nonstop4h 33m
United Airlines
Deal found 5/12![United Airlines logo]()
$448
This American Airlines deal was found by Cheapflights users on 5/12. 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 6/1312:41 pm
ONT
- PIA
1 stop8h 52m
American Airlines
Mon 6/154:20 pm
PIA
- ONT
1 stop8h 16m
American Airlines
Deal found 5/12![American Airlines logo]()
$550
This Kiwi.com deal was found by Cheapflights users on 5/13. 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 6/38:17 pm
ONT
- RFD
2 stops14h 06m
Multiple Airlines
Sun 6/71:13 pm
RFD
- ONT
1 stop27h 56m
Multiple Airlines
Deal found 5/13![Multiple Airlines logo]()
$516
This Southwest deal was found by Cheapflights users on 5/14. 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 6/98:15 am
ONT
- MDW
2 stops6h 45m
Southwest
Wed 6/247:00 am
MDW
- ONT
2 stops7h 55m
Southwest
Deal found 5/14![Southwest logo]()
$433
This Delta deal was found by Cheapflights users on 5/14. 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 7/3011:48 am
ONT
- MLI
1 stop8h 43m
Delta
Sat 8/1511:08 am
MLI
- ONT
1 stop9h 21m
Delta
Deal found 5/14![Delta logo]()
$449
This United Airlines deal was found by Cheapflights users on 5/10. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 8/66:10 am
ONT
- ORD
Nonstop4h 15m
United Airlines
Wed 8/125:55 am
ORD
- ONT
1 stop8h 55m
United Airlines
Deal found 5/10![United Airlines logo]()
$458
This American Airlines deal was found by Cheapflights users on 5/12. 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 7/11:11 pm
ONT
- SPI
2 stops8h 56m
American Airlines
Thu 7/92:55 pm
SPI
- ONT
2 stops11h 04m
American Airlines
Deal found 5/12![American Airlines logo]()
$556
This Kiwi.com deal was found by Cheapflights users on 5/14. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 6/123:34 pm
ONT
- RFD
2 stops18h 40m
Multiple Airlines
Sun 6/141:13 pm
RFD
- ONT
1 stop8h 38m
Multiple Airlines
Deal found 5/14![Multiple Airlines logo]()
$518
Last-minute flights from Ontario to IllinoisDiscover last-minute flight deals from Ontario to Illinois. Data last updated May 15, 2026 and is based on user searches.
Discover last-minute flight deals from Ontario to Illinois. Data last updated May 15, 2026 and is based on user searches.
This Frontier deal was found by Cheapflights users on 5/12. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 5/266:00 am
ONT
- STL
1 stop11h 23m
Frontier
Sat 6/68:08 pm
STL
- ONT
1 stop5h 41m
Frontier
Deal found 5/12![Frontier logo]()
$234
This Travelocity deal was found by Cheapflights users on 5/12. 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 Travelocity is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 5/266:00 am
ONT
- STL
1 stop11h 23m
Frontier
Sun 5/319:06 pm
STL
- ONT
1 stop24h 26m
Frontier
Deal found 5/12![Frontier logo]()
$250
This Frontier deal was found by Cheapflights users on 5/12. 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 5/2810:50 am
ONT
- STL
1 stop6h 33m
Frontier
Sat 6/68:08 pm
STL
- ONT
1 stop5h 41m
Frontier
Deal found 5/12![Frontier logo]()
$254
This Booking.com deal was found by Cheapflights users on 5/10. 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 6/111:51 am
ONT
- STL
1 stop6h 20m
Frontier
Fri 6/59:06 pm
STL
- ONT
1 stop24h 26m
Frontier
Deal found 5/10![Frontier logo]()
$252
This Frontier deal was found by Cheapflights users on 5/11. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 6/26:00 am
ONT
- STL
1 stop11h 23m
Frontier
Wed 6/38:08 pm
STL
- ONT
1 stop5h 41m
Frontier
Deal found 5/11![Frontier logo]()
$230
This CheapOair deal was found by Cheapflights users on 5/13. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure CheapOair is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 6/34:39 pm
ONT
- STL
1 stop25h 32m
Frontier
Sat 6/68:08 pm
STL
- ONT
1 stop15h 57m
Frontier
Deal found 5/13![Frontier logo]()
$224
This Delta deal was found by Cheapflights users on 5/13. 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 6/311:52 am
ONT
- ORD
1 stop10h 03m
Delta
Sat 6/612:30 pm
ORD
- ONT
2 stops11h 18m
Delta
Deal found 5/13![Delta logo]()
$277
This Frontier deal was found by Cheapflights users on 5/11. 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 6/411:51 am
ONT
- STL
1 stop6h 20m
Frontier
Mon 6/88:08 pm
STL
- ONT
1 stop5h 41m
Frontier
Deal found 5/11![Frontier logo]()
$244
This Super.com deal was found by Cheapflights users on 5/12. 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 6/66:00 am
ONT
- ORD
1 stop12h 32m
Frontier
Mon 6/89:37 pm
ORD
- ONT
1 stop14h 28m
Frontier
Deal found 5/12![Frontier logo]()
$278
This Expedia deal was found by Cheapflights users on 5/12. 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.
Tue 6/93:34 pm
ONT
- STL
1 stop24h 34m
Frontier
Tue 6/238:08 pm
STL
- ONT
1 stop5h 41m
Frontier
Deal found 5/12![Frontier logo]()
$210
This Trip.com deal was found by Cheapflights users on 5/12. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Trip.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 6/101:33 pm
ONT
- STL
1 stop22h 33m
Frontier
Wed 6/177:46 pm
STL
- ONT
1 stop21h 22m
Frontier
Deal found 5/12![Frontier logo]()
$226
This Booking.com deal was found by Cheapflights users on 5/10. 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 6/101:33 pm
ONT
- STL
1 stop22h 33m
Frontier
Mon 6/152:56 pm
STL
- ONT
1 stop6h 55m
Frontier
Deal found 5/10![Frontier logo]()
$232
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 May 15, 2026.
Search for one-way flight options from Ontario to Illinois. Find affordable one-way fares based on user searches. Data last updated May 15, 2026.
This Trip.com deal was found by Cheapflights users on 5/15. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Trip.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 8/126:00 am
ONT
- ORD
1 stop12h 52m
Frontier
Deal found 5/15![Frontier logo]()
$80
This Kiwi.com deal was found by Cheapflights users on 5/12. 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 6/26:00 am
ONT
- STL
1 stop11h 23m
Frontier
Deal found 5/12![Frontier logo]()
$82
This Kiwi.com deal was found by Cheapflights users on 5/13. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 7/213:40 pm
ONT
- ORD
1 stop11h 48m
Frontier
Deal found 5/13![Frontier logo]()
$99
This Kiwi.com deal was found by Cheapflights users on 5/11. 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 6/233:34 pm
ONT
- ORD
1 stop11h 33m
Frontier
Deal found 5/11![Frontier logo]()
$102
This Frontier deal was found by Cheapflights users on 5/11. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 9/110:50 am
ONT
- STL
1 stop6h 33m
Frontier
Deal found 5/11![Frontier logo]()
$105
This United Airlines deal was found by Cheapflights users on 5/10. 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 7/281:50 pm
ONT
- ORD
1 stop9h 09m
United Airlines
Deal found 5/10![United Airlines logo]()
$105
This Super.com deal was found by Cheapflights users on 5/12. 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 6/101:33 pm
ONT
- STL
1 stop22h 33m
Frontier
Deal found 5/12![Frontier logo]()
$106
This Super.com deal was found by Cheapflights users on 5/12. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 7/153:40 pm
ONT
- ORD
1 stop11h 48m
Frontier
Deal found 5/12![Frontier logo]()
$106
This Trip.com deal was found by Cheapflights users on 5/10. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Trip.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 6/36:00 am
ONT
- ORD
1 stop12h 32m
Frontier
Deal found 5/10![Frontier logo]()
$107
This Kiwi.com deal was found by Cheapflights users on 5/14. 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 10/1711:38 am
ONT
- ORD
1 stop20h 23m
Frontier
Deal found 5/14![Frontier logo]()
$109
This Super.com deal was found by Cheapflights users on 5/11. 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 6/301:33 pm
ONT
- STL
1 stop27h 18m
Frontier
Deal found 5/11![Frontier logo]()
$110
This Southwest deal was found by Cheapflights users on 5/15. 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 8/1211:55 pm
ONT
- MDW
Nonstop3h 50m
Southwest
Deal found 5/15![Southwest logo]()
$110
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 May 15, 2026.
Most accurate provider | FlightHub 3 stars |
|---|---|
Most trusted provider | FlightHub 3 stars |
Round-trip from | $185 (Trip.com) |
One-way from | $80 (Trip.com) |
Popular in | February |
Cheapest in | September |
Average price | $319 |
Good round-trip deal | $411 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 May 15, 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
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
Thu 9/17
8:07 am-5:44 pm
1 stop7h 37m
Lambert-St Louis
Mon 9/21
8:10 pm-11:55 pm
1 stop5h 45m
$216
OntarioChicago
ONT - ORD
ONTORD
Ontario
Mon 10/26
6:54 pm-6:20 am
1 stop9h 26m
Chicago O'Hare Intl
Wed 10/28
9:00 am-6:00 pm
1 stop11h 00m
$307
OntarioChicago
ONT - MDW
ONTMDW
Ontario
Wed 7/8
10:00 pm-12:38 pm
2 stops12h 38m
Chicago Midway
Wed 7/15
1:18 pm-11:48 pm
2 stops12h 30m
$308
OntarioChicago
ONT - MDW
ONTMDW
Ontario
Wed 7/8
5:30 am-1:25 pm
1 stop5h 55m
Chicago Midway
Wed 7/15
10:10 am-3:30 pm
2 stops7h 20m
$329
Quickest round-trip
OntarioChicago
ONT - ORD
ONTORD
Ontario
Sat 7/18
6:10 am-12:25 pm
Nonstop4h 15m
Chicago O'Hare Intl
Wed 7/22
8:18 pm-10:51 pm
Nonstop4h 33m
$348
OntarioChicago
ONT - MDW
ONTMDW
Ontario
Sat 8/1
11:55 pm-5:40 am
Nonstop3h 45m
Chicago Midway
Tue 8/4
5:15 pm-10:05 pm
1 stop6h 50m
$358
OntarioBloomington
ONT - BMI
ONTBMI
Ontario
Wed 10/14
12:00 pm-10:23 pm
1 stop8h 23m
Bloomington-Normal
Tue 10/20
4:00 pm-10:14 pm
1 stop8h 14m
$359
OntarioBloomington
ONT - BMI
ONTBMI
Ontario
Fri 10/16
12:00 pm-10:23 pm
1 stop8h 23m
Bloomington-Normal
Mon 10/19
4:00 pm-10:14 pm
1 stop8h 14m
$359
OntarioMoline
ONT - MLI
ONTMLI
Ontario
Wed 5/27
12:07 pm-10:21 pm
1 stop8h 14m
Moline Quad-City
Sat 5/30
5:56 am-4:17 pm
2 stops12h 21m
$380
OntarioChicago
ONT - ORD
ONTORD
Ontario
Thu 8/20
1:18 pm-10:46 pm
1 stop7h 28m
Chicago O'Hare Intl
Tue 8/25
7:00 am-12:50 pm
1 stop7h 50m
$393
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-MDW
ONT-ORD
ONT-RFD
ONT-STL
ONT-MLI
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-MDW
ONT-ORD
ONT-RFD
ONT-STL
How far ahead should I book a flight from Ontario to Illinois?
The best time to book flights from Ontario to Illinois is 73 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 Illinois?
Currently, September is the cheapest month in which you can book a flight from Ontario to Illinois (average of $102). 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 May 15, 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 May 15, 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.
Overall
8.0
Food
7.0
Boarding
8.1
Crew
8.6
Entertainment
7.5
Comfort
8.0
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Overall
8.0
Food
7.0
Boarding
8.1
Crew
8.6
Entertainment
7.5
Comfort
8.0
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Overall
8.0
Food
7.0
Boarding
8.1
Crew
8.6
Entertainment
7.5
Comfort
8.0
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Overall
8.0
Food
7.0
Boarding
8.1
Crew
8.6
Entertainment
7.5
Comfort
8.0
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Overall
8.0
Food
7.0
Boarding
8.1
Crew
8.6
Entertainment
7.5
Comfort
8.0
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Overall
8.0
Food
7.0
Boarding
8.1
Crew
8.6
Entertainment
7.5
Comfort
8.0
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.
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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 May 15, 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 May 15, 2026.
| Airline | Cheapest | Average | Flexibility | On-time |
|---|---|---|---|---|
| Cheapest$117 | Average$257 | FlexibilityNo cancel fee | On-time62% | |
| Cheapest$226 | Average$465 | FlexibilityNo cancel fee | On-time69% | |
| Cheapest$258 | Average$434 | FlexibilityNo cancel fee | On-time63% | |
| Cheapest$260 | Average$447 | FlexibilityNo cancel fee | On-timeN/A | |
| Cheapest$288 | Average$492 | FlexibilityNo cancel fee | On-time71% |