$99+ 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
Aug 2 — Aug 91
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 July 3, 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 July 3, 2026.
This Kiwi.com deal was found by Cheapflights users on 7/2. Clicking the “Pick Dates” 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 8/116:00 am
ONT
- STL
1 stop11h 23m
Frontier
Tue 8/188:00 am
STL
- ONT
1 stop9h 54m
Frontier
Deal found 7/2![Frontier logo]()
$215
This Kiwi.com deal was found by Cheapflights users on 6/30. Clicking the “Pick Dates” 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 7/2810:49 am
ONT
- STL
1 stop6h 34m
Frontier
Tue 8/48:08 pm
STL
- ONT
1 stop15h 56m
Frontier
Deal found 6/30![Frontier logo]()
$218
This Frontier deal was found by Cheapflights users on 7/1. Clicking the “Pick Dates” 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 8/116:00 am
ONT
- STL
1 stop11h 23m
Frontier
Wed 8/128:08 pm
STL
- ONT
1 stop5h 42m
Frontier
Deal found 7/1![Frontier logo]()
$248
This Kiwi.com deal was found by Cheapflights users on 6/30. Clicking the “Pick Dates” 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 8/56:00 am
ONT
- STL
1 stop11h 23m
Frontier
Sun 8/97:10 pm
STL
- ONT
1 stop14h 53m
Frontier
Deal found 6/30![Frontier logo]()
$250
This Expedia deal was found by Cheapflights users on 7/2. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Expedia is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 7/236:00 am
ONT
- STL
1 stop11h 23m
Frontier
Tue 7/287:03 pm
STL
- ONT
1 stop15h 00m
Frontier
Deal found 7/2![Frontier logo]()
$256
This CheapOair deal was found by Cheapflights users on 7/2. Clicking the “Pick Dates” 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 7/293:40 pm
ONT
- STL
1 stop24h 35m
Frontier
Sat 8/17:10 pm
STL
- ONT
1 stop14h 53m
Frontier
Deal found 7/2![Frontier logo]()
$258
This Kiwi.com deal was found by Cheapflights users on 7/2. Clicking the “Pick Dates” 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 8/68:17 am
ONT
- STL
2 stops22h 40m
Frontier
Tue 8/118:08 pm
STL
- ONT
1 stop15h 56m
Frontier
Deal found 7/2![Frontier logo]()
$265
This CheapOair deal was found by Cheapflights users on 7/2. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure CheapOair is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sun 7/266:00 am
ONT
- STL
1 stop11h 23m
Frontier
Wed 7/297:03 pm
STL
- ONT
1 stop22h 51m
Frontier
Deal found 7/2![Frontier logo]()
$266
This Booking.com deal was found by Cheapflights users on 7/3. Clicking the “Pick Dates” 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 7/223:40 pm
ONT
- STL
1 stop24h 35m
Frontier
Tue 7/287:03 pm
STL
- ONT
1 stop15h 00m
Frontier
Deal found 7/3![Frontier logo]()
$269
This Expedia deal was found by Cheapflights users on 7/3. Clicking the “Pick Dates” 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.
Sat 8/16:00 am
ONT
- ORD
1 stop12h 52m
Frontier
Tue 8/49:34 pm
ORD
- ONT
1 stop13h 07m
Frontier
Deal found 7/3![Frontier logo]()
$280
This Booking.com deal was found by Cheapflights users on 7/1. Clicking the “Pick Dates” 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 7/2810:49 am
ONT
- ORD
1 stop8h 03m
Frontier
Fri 7/315:46 pm
ORD
- ONT
1 stop15h 46m
Frontier
Deal found 7/1![Frontier logo]()
$281
This Mytrip deal was found by Cheapflights users on 7/2. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Mytrip is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 7/256:00 am
ONT
- ORD
1 stop12h 52m
Frontier
Mon 8/39:57 pm
ORD
- ONT
1 stop14h 07m
Frontier
Deal found 7/2![Frontier logo]()
$282
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 July 3, 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 July 3, 2026.
This Booking.com deal was found by Cheapflights users on 7/2. Clicking the “Pick Dates” 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 7/313:40 pm
ONT
- STL
1 stop24h 35m
Frontier
Tue 8/48:08 pm
STL
- ONT
1 stop5h 42m
Frontier
Deal found 7/2![Frontier logo]()
$264
This Southwest deal was found by Cheapflights users on 7/1. Clicking the “Pick Dates” 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 11/77:00 am
ONT
- MDW
2 stops8h 05m
Southwest
Mon 11/95:15 am
MDW
- ONT
1 stop8h 15m
Southwest
Deal found 7/1![Southwest logo]()
$293
This Delta deal was found by Cheapflights users on 7/2. Clicking the “Pick Dates” 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 10/67:05 am
ONT
- MDW
1 stop7h 15m
Delta
Wed 10/211:28 pm
MDW
- ONT
2 stops11h 15m
Delta
Deal found 7/2![Delta logo]()
$314
This Kiwi.com deal was found by Cheapflights users on 7/3. Clicking the “Pick Dates” 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 9/309:49 pm
ONT
- RFD
1 stop20h 24m
Multiple Airlines
Sun 10/49:36 pm
RFD
- ONT
1 stop14h 45m
Multiple Airlines
Deal found 7/3![Multiple Airlines logo]()
$317
This American Airlines deal was found by Cheapflights users on 6/29. Clicking the “Pick Dates” 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.
Thu 7/3011:59 pm
ONT
- MLI
1 stop8h 40m
American Airlines
Tue 8/44:45 pm
MLI
- ONT
1 stop9h 14m
American Airlines
Deal found 6/29![American Airlines logo]()
$340
This United Airlines deal was found by Cheapflights users on 7/2. Clicking the “Pick Dates” 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 8/81:18 pm
ONT
- ORD
1 stop7h 31m
United Airlines
Sat 8/158:06 pm
ORD
- ONT
Nonstop4h 29m
United Airlines
Deal found 7/2![United Airlines logo]()
$350
This Alaska Airlines deal was found by Cheapflights users on 6/30. Clicking the “Pick Dates” 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 8/1310:54 am
ONT
- ORD
1 stop16h 06m
Alaska Airlines
Mon 8/176:00 am
ORD
- ONT
2 stops14h 03m
Alaska Airlines
Deal found 6/30![Alaska Airlines logo]()
$466
This Southwest deal was found by Cheapflights users on 6/28. Clicking the “Pick Dates” 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.
Thu 10/228:00 pm
ONT
- MDW
1 stop8h 00m
Southwest
Mon 10/269:55 am
MDW
- ONT
2 stops7h 25m
Southwest
Deal found 6/28![Southwest logo]()
$322
This Kiwi.com deal was found by Cheapflights users on 7/1. Clicking the “Pick Dates” 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 9/99:49 pm
ONT
- RFD
1 stop20h 50m
Multiple Airlines
Sun 9/139:29 pm
RFD
- ONT
1 stop14h 52m
Multiple Airlines
Deal found 7/1![Multiple Airlines logo]()
$337
This American Airlines deal was found by Cheapflights users on 6/29. Clicking the “Pick Dates” 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 9/212:33 pm
ONT
- MLI
1 stop7h 38m
American Airlines
Sun 9/67:33 am
MLI
- ONT
1 stop6h 10m
American Airlines
Deal found 6/29![American Airlines logo]()
$340
This Delta deal was found by Cheapflights users on 7/1. Clicking the “Pick Dates” 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 8/266:20 am
ONT
- ORD
1 stop8h 40m
Delta
Fri 8/287:44 pm
ORD
- ONT
1 stop5h 50m
Delta
Deal found 7/1![Delta logo]()
$363
This United Airlines deal was found by Cheapflights users on 6/28. Clicking the “Pick Dates” 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 8/101:50 pm
ONT
- ORD
1 stop9h 09m
United Airlines
Wed 8/198:06 pm
ORD
- ONT
Nonstop4h 29m
United Airlines
Deal found 6/28![United Airlines logo]()
$375
This Frontier deal was found by Cheapflights users on 6/30. Clicking the “Pick Dates” 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 7/76:00 am
ONT
- STL
1 stop11h 23m
Frontier
Thu 7/168:08 pm
STL
- ONT
1 stop5h 42m
Frontier
Deal found 6/30![Frontier logo]()
$378
This Kiwi.com deal was found by Cheapflights users on 6/29. Clicking the “Pick Dates” 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 10/111:16 am
ONT
- RFD
1 stop6h 57m
Multiple Airlines
Sun 10/49:36 pm
RFD
- ONT
1 stop14h 45m
Multiple Airlines
Deal found 6/29![Multiple Airlines logo]()
$349
This Southwest deal was found by Cheapflights users on 7/1. Clicking the “Pick Dates” 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 7/294:35 pm
ONT
- MDW
1 stop5h 35m
Southwest
Wed 8/56:00 am
MDW
- ONT
1 stop8h 30m
Southwest
Deal found 7/1![Southwest logo]()
$363
This Delta deal was found by Cheapflights users on 6/28. Clicking the “Pick Dates” 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 8/136:00 am
ONT
- STL
1 stop5h 38m
Delta
Sat 8/155:00 pm
STL
- ONT
1 stop7h 23m
Delta
Deal found 6/28![Delta logo]()
$367
This United Airlines deal was found by Cheapflights users on 6/29. Clicking the “Pick Dates” 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 8/247:13 pm
ONT
- ORD
1 stop7h 51m
United Airlines
Fri 9/48:06 pm
ORD
- ONT
Nonstop4h 29m
United Airlines
Deal found 6/29![United Airlines logo]()
$382
This Delta deal was found by Cheapflights users on 6/28. Clicking the “Pick Dates” 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 8/135:05 pm
ONT
- STL
1 stop5h 36m
Delta
Mon 8/177:45 pm
STL
- ONT
1 stop5h 49m
Delta
Deal found 6/28![Delta logo]()
$367
This Kiwi.com deal was found by Cheapflights users on 6/30. Clicking the “Pick Dates” 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 8/183:40 pm
ONT
- RFD
2 stops19h 43m
Multiple Airlines
Thu 8/209:35 pm
RFD
- ONT
1 stop12h 28m
Multiple Airlines
Deal found 6/30![Multiple Airlines logo]()
$368
This American Airlines deal was found by Cheapflights users on 7/3. Clicking the “Pick Dates” 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.
Fri 7/317:15 pm
ONT
- MLI
2 stops13h 24m
American Airlines
Fri 8/74:32 pm
MLI
- ONT
1 stop8h 27m
American Airlines
Deal found 7/3![American Airlines logo]()
$419
This Southwest deal was found by Cheapflights users on 6/28. Clicking the “Pick Dates” 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 8/1511:00 am
ONT
- MDW
2 stops7h 15m
Southwest
Mon 8/178:00 am
MDW
- ONT
2 stops9h 05m
Southwest
Deal found 6/28![Southwest logo]()
$402
This Delta deal was found by Cheapflights users on 6/28. Clicking the “Pick Dates” 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 8/135:05 pm
ONT
- STL
1 stop5h 36m
Delta
Tue 8/187:45 pm
STL
- ONT
1 stop5h 49m
Delta
Deal found 6/28![Delta logo]()
$367
This United Airlines deal was found by Cheapflights users on 6/29. Clicking the “Pick Dates” 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 8/117:00 am
ONT
- ORD
Nonstop4h 10m
United Airlines
Sun 8/168:06 pm
ORD
- ONT
Nonstop4h 29m
United Airlines
Deal found 6/29![United Airlines logo]()
$443
This Delta deal was found by Cheapflights users on 6/30. Clicking the “Pick Dates” 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 8/136:00 am
ONT
- STL
1 stop5h 38m
Delta
Wed 8/197:45 pm
STL
- ONT
1 stop5h 49m
Delta
Deal found 6/30![Delta logo]()
$367
This American Airlines deal was found by Cheapflights users on 6/28. Clicking the “Pick Dates” 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.
Fri 7/172:15 pm
ONT
- MLI
1 stop7h 15m
American Airlines
Mon 7/204:45 pm
MLI
- ONT
1 stop7h 47m
American Airlines
Deal found 6/28![American Airlines logo]()
$449
This Southwest deal was found by Cheapflights users on 6/30. Clicking the “Pick Dates” 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 8/315:15 am
ONT
- STL
2 stops10h 05m
Southwest
Thu 10/18:25 am
STL
- ONT
2 stops7h 35m
Southwest
Deal found 6/30![Southwest logo]()
$413
This Kiwi.com deal was found by Cheapflights users on 6/29. Clicking the “Pick Dates” 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 9/311:15 am
ONT
- RFD
1 stop7h 24m
Multiple Airlines
Thu 9/109:29 pm
RFD
- ONT
1 stop14h 52m
Multiple Airlines
Deal found 6/29![Multiple Airlines logo]()
$436
This Delta deal was found by Cheapflights users on 6/30. Clicking the “Pick Dates” 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 8/105:05 pm
ONT
- STL
1 stop5h 36m
Delta
Wed 8/198:00 am
STL
- ONT
1 stop6h 16m
Delta
Deal found 6/30![Delta logo]()
$367
This United Airlines deal was found by Cheapflights users on 7/2. Clicking the “Pick Dates” 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 11/101:13 pm
ONT
- PIA
1 stop5h 34m
United Airlines
Sat 11/148:50 am
PIA
- ONT
1 stop5h 52m
United Airlines
Deal found 7/2![United Airlines logo]()
$449
This Kiwi.com deal was found by Cheapflights users on 6/30. Clicking the “Pick Dates” 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 7/153:40 pm
ONT
- MLI
1 stop18h 01m
Multiple Airlines
Sun 7/1912:31 pm
MLI
- ONT
1 stop21h 32m
Multiple Airlines
Deal found 6/30![Multiple Airlines logo]()
$439
Last-minute flights from Ontario to IllinoisDiscover last-minute flight deals from Ontario to Illinois. Data last updated July 3, 2026 and is based on user searches.
Discover last-minute flight deals from Ontario to Illinois. Data last updated July 3, 2026 and is based on user searches.
This Booking.com deal was found by Cheapflights users on 7/3. Clicking the “Pick Dates” 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 7/223:40 pm
ONT
- STL
1 stop24h 35m
Frontier
Tue 7/287:03 pm
STL
- ONT
1 stop15h 00m
Frontier
Deal found 7/3![Frontier logo]()
$269
This Expedia deal was found by Cheapflights users on 7/2. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Expedia is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 7/236:00 am
ONT
- STL
1 stop11h 23m
Frontier
Tue 7/287:03 pm
STL
- ONT
1 stop15h 00m
Frontier
Deal found 7/2![Frontier logo]()
$256
This Mytrip deal was found by Cheapflights users on 7/2. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Mytrip is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 7/256:00 am
ONT
- ORD
1 stop12h 52m
Frontier
Mon 8/39:57 pm
ORD
- ONT
1 stop14h 07m
Frontier
Deal found 7/2![Frontier logo]()
$282
This CheapOair deal was found by Cheapflights users on 7/2. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure CheapOair is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sun 7/266:00 am
ONT
- STL
1 stop11h 23m
Frontier
Wed 7/297:03 pm
STL
- ONT
1 stop22h 51m
Frontier
Deal found 7/2![Frontier logo]()
$266
This Kiwi.com deal was found by Cheapflights users on 6/30. Clicking the “Pick Dates” 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 7/2810:49 am
ONT
- STL
1 stop6h 34m
Frontier
Tue 8/48:08 pm
STL
- ONT
1 stop15h 56m
Frontier
Deal found 6/30![Frontier logo]()
$218
This Booking.com deal was found by Cheapflights users on 7/1. Clicking the “Pick Dates” 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 7/2810:49 am
ONT
- ORD
1 stop8h 03m
Frontier
Fri 7/315:46 pm
ORD
- ONT
1 stop15h 46m
Frontier
Deal found 7/1![Frontier logo]()
$281
This CheapOair deal was found by Cheapflights users on 7/2. Clicking the “Pick Dates” 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 7/293:40 pm
ONT
- STL
1 stop24h 35m
Frontier
Sat 8/17:10 pm
STL
- ONT
1 stop14h 53m
Frontier
Deal found 7/2![Frontier logo]()
$258
This Expedia deal was found by Cheapflights users on 7/3. Clicking the “Pick Dates” 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.
Sat 8/16:00 am
ONT
- ORD
1 stop12h 52m
Frontier
Tue 8/49:34 pm
ORD
- ONT
1 stop13h 07m
Frontier
Deal found 7/3![Frontier logo]()
$280
This Kiwi.com deal was found by Cheapflights users on 6/30. Clicking the “Pick Dates” 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 8/56:00 am
ONT
- STL
1 stop11h 23m
Frontier
Sun 8/97:10 pm
STL
- ONT
1 stop14h 53m
Frontier
Deal found 6/30![Frontier logo]()
$250
This Kiwi.com deal was found by Cheapflights users on 7/2. Clicking the “Pick Dates” 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 8/68:17 am
ONT
- STL
2 stops22h 40m
Frontier
Tue 8/118:08 pm
STL
- ONT
1 stop15h 56m
Frontier
Deal found 7/2![Frontier logo]()
$265
This Kiwi.com deal was found by Cheapflights users on 7/2. Clicking the “Pick Dates” 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 8/116:00 am
ONT
- STL
1 stop11h 23m
Frontier
Tue 8/188:00 am
STL
- ONT
1 stop9h 54m
Frontier
Deal found 7/2![Frontier logo]()
$215
This Frontier deal was found by Cheapflights users on 7/1. Clicking the “Pick Dates” 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 8/116:00 am
ONT
- STL
1 stop11h 23m
Frontier
Wed 8/128:08 pm
STL
- ONT
1 stop5h 42m
Frontier
Deal found 7/1![Frontier logo]()
$248
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 July 3, 2026.
Search for one-way flight options from Ontario to Illinois. Find affordable one-way fares based on user searches. Data last updated July 3, 2026.
This Trip.com deal was found by Cheapflights users on 7/1. Clicking the “Pick Dates” 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 7/1![Frontier logo]()
$99
This Kiwi.com deal was found by Cheapflights users on 6/30. Clicking the “Pick Dates” 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 9/17:56 pm
ONT
- ORD
1 stop15h 40m
Frontier
Deal found 6/30![Frontier logo]()
$101
This Kiwi.com deal was found by Cheapflights users on 7/1. Clicking the “Pick Dates” 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 8/187:56 pm
ONT
- ORD
1 stop15h 40m
Frontier
Deal found 7/1![Frontier logo]()
$102
This Trip.com deal was found by Cheapflights users on 7/3. Clicking the “Pick Dates” 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 9/126:00 am
ONT
- ORD
1 stop13h 35m
Frontier
Deal found 7/3![Frontier logo]()
$105
This Trip.com deal was found by Cheapflights users on 6/29. Clicking the “Pick Dates” 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 8/16:00 am
ONT
- STL
1 stop11h 23m
Frontier
Deal found 6/29![Frontier logo]()
$108
This Trip.com deal was found by Cheapflights users on 6/30. Clicking the “Pick Dates” 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 7/286:00 am
ONT
- ORD
1 stop12h 52m
Frontier
Deal found 6/30![Frontier logo]()
$108
This Trip.com deal was found by Cheapflights users on 6/29. Clicking the “Pick Dates” 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 8/116:00 am
ONT
- ORD
1 stop12h 52m
Frontier
Deal found 6/29![Frontier logo]()
$109
This Super.com deal was found by Cheapflights users on 7/1. Clicking the “Pick Dates” 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 8/18:17 am
ONT
- MDW
1 stop7h 09m
Frontier
Deal found 7/1![Frontier logo]()
$118
This Southwest deal was found by Cheapflights users on 7/2. Clicking the “Pick Dates” 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 9/111:55 pm
ONT
- MDW
Nonstop3h 50m
Southwest
Deal found 7/2![Southwest logo]()
$120
This United Airlines deal was found by Cheapflights users on 6/29. Clicking the “Pick Dates” 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 8/117:00 am
ONT
- ORD
Nonstop4h 10m
United Airlines
Deal found 6/29![United Airlines logo]()
$120
This Frontier deal was found by Cheapflights users on 7/1. Clicking the “Pick Dates” 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 7/2810:49 am
ONT
- STL
1 stop6h 34m
Frontier
Deal found 7/1![Frontier logo]()
$124
This Trip.com deal was found by Cheapflights users on 7/1. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Trip.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 8/178:17 am
ONT
- MDW
1 stop7h 05m
Frontier
Deal found 7/1![Frontier logo]()
$124
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 July 3, 2026.
Most accurate provider | FlightHub 3 stars |
|---|---|
Most trusted provider | FlightHub 3 stars |
Round-trip from | $215 (Kiwi.com) |
One-way from | $99 (Trip.com) |
Popular in | June |
Cheapest in | September |
Average price | $356 |
Good round-trip deal | $415 or less |
Good one-way deal | $249 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 July 3, 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
Fri 7/31
3:40 pm-6:15 pm
1 stop24h 35m
Lambert-St Louis
Tue 8/4
8:08 pm-11:50 pm
1 stop5h 42m
$264
OntarioChicago
ONT - MDW
ONTMDW
Ontario
Sat 11/7
7:00 am-5:05 pm
2 stops8h 05m
Chicago Midway
Mon 11/9
5:15 am-11:30 am
1 stop8h 15m
$293
OntarioChicago
ONT - MDW
ONTMDW
Ontario
Tue 10/6
7:05 am-4:20 pm
1 stop7h 15m
Chicago Midway
Wed 10/21
1:28 pm-10:43 pm
2 stops11h 15m
$314
OntarioChicago
ONT - RFD
ONTRFD
Ontario
Wed 9/30
9:49 pm-8:13 pm
1 stop20h 24m
Chicago Greater Rockford
Sun 10/4
9:36 pm-10:21 am
1 stop14h 45m
$317
OntarioChicago
ONT - MDW
ONTMDW
Ontario
Thu 10/22
8:00 pm-6:00 am
1 stop8h 00m
Chicago Midway
Mon 10/26
9:55 am-3:20 pm
2 stops7h 25m
$322
OntarioChicago
ONT - RFD
ONTRFD
Ontario
Wed 9/9
9:49 pm-8:39 pm
1 stop20h 50m
Chicago Greater Rockford
Sun 9/13
9:29 pm-10:21 am
1 stop14h 52m
$337
OntarioMoline
ONT - MLI
ONTMLI
Ontario
Thu 7/30
11:59 pm-10:39 am
1 stop8h 40m
Moline Quad-City
Tue 8/4
4:45 pm-11:59 pm
1 stop9h 14m
$340
OntarioMoline
ONT - MLI
ONTMLI
Ontario
Wed 9/2
12:33 pm-10:11 pm
1 stop7h 38m
Moline Quad-City
Sun 9/6
7:33 am-11:43 am
1 stop6h 10m
$340
OntarioChicago
ONT - RFD
ONTRFD
Ontario
Thu 10/1
11:16 am-8:13 pm
1 stop6h 57m
Chicago Greater Rockford
Sun 10/4
9:36 pm-10:21 am
1 stop14h 45m
$349
OntarioChicago
ONT - ORD
ONTORD
Ontario
Sat 8/8
1:18 pm-10:49 pm
1 stop7h 31m
Chicago O'Hare Intl
Sat 8/15
8:06 pm-10:35 pm
Nonstop4h 29m
$350
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-ORD
ONT-MDW
ONT-RFD
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-STL
ONT-ORD
ONT-MDW
ONT-RFD
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 July 3, 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?
How far ahead should I book a flight from Ontario to Illinois?
The best time to book flights from Ontario to Illinois is 74 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.
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 July 3, 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.
Comfort
8.0
Food
7.0
Entertainment
7.5
Overall
7.9
Boarding
8.1
Crew
8.6
Reviews
1 / 20
6.0
GoodReza,Jun 2026
TPA - MDW
Comfort
8.0
Food
7.0
Entertainment
7.5
Overall
7.9
Boarding
8.1
Crew
8.6
Reviews
1 / 20
6.0
GoodReza,Jun 2026
TPA - MDW
Comfort
8.0
Food
7.0
Entertainment
7.5
Overall
7.9
Boarding
8.1
Crew
8.6
Reviews
1 / 20
6.0
GoodReza,Jun 2026
TPA - MDW
Comfort
8.0
Food
7.0
Entertainment
7.5
Overall
7.9
Boarding
8.1
Crew
8.6
Reviews
1 / 20
6.0
GoodReza,Jun 2026
TPA - MDW
Comfort
8.0
Food
7.0
Entertainment
7.5
Overall
7.9
Boarding
8.1
Crew
8.6
Reviews
1 / 20
6.0
GoodReza,Jun 2026
TPA - MDW
Comfort
8.0
Food
7.0
Entertainment
7.5
Overall
7.9
Boarding
8.1
Crew
8.6
Reviews
1 / 20
6.0
GoodReza,Jun 2026
TPA - MDW
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 July 3, 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 July 3, 2026.
| Airline | Cheapest | Average | Flexibility | On-time |
|---|---|---|---|---|
| Cheapest$117 | Average$259 | FlexibilityNo cancel fee | On-time62% | |
| Cheapest$256 | Average$456 | FlexibilityNo cancel fee | On-time69% | |
| Cheapest$258 | Average$428 | FlexibilityNo cancel fee | On-time63% | |
| Cheapest$260 | Average$446 | FlexibilityNo cancel fee | On-timeN/A | |
| Cheapest$276 | Average$474 | FlexibilityNo cancel fee | On-time71% |