$67+ 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 5/3. Fares are subject to change and may not be available on all flights or dates of travel.
ONT — ORD
May 8 — May 151
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 8, 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 8, 2026.
This Kiwi.com deal was found by Cheapflights users on 4/7. Clicking the “Pick Dates” 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 5/15:33 pm
ONT
- STL
1 stop23h 59m
Frontier
Mon 5/48:17 pm
STL
- ONT
1 stop15h 48m
Frontier
Deal found 4/7![Frontier logo]()
$135
This Kiwi.com deal was found by Cheapflights users on 4/5. Clicking the “Pick Dates” 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 4/2412:59 am
ONT
- STL
1 stop16h 33m
Frontier
Mon 4/278:17 pm
STL
- ONT
1 stop29h 38m
Frontier
Deal found 4/5![Frontier logo]()
$137
This Trip.com deal was found by Cheapflights users on 4/6. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Trip.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 5/112:59 am
ONT
- STL
1 stop16h 33m
Frontier
Thu 5/712:36 pm
STL
- ONT
1 stop8h 56m
Frontier
Deal found 4/6![Frontier logo]()
$157
This Frontier deal was found by Cheapflights users on 4/3. 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 Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 4/245:33 pm
ONT
- STL
1 stop23h 59m
Frontier
Sat 5/28:17 pm
STL
- ONT
1 stop13h 09m
Frontier
Deal found 4/3![Frontier logo]()
$160
This Booking.com deal was found by Cheapflights users on 4/6. Clicking the “Pick Dates” 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 5/54:39 pm
ONT
- STL
1 stop23h 27m
Frontier
Fri 5/89:18 pm
STL
- ONT
1 stop19h 51m
Frontier
Deal found 4/6![Frontier logo]()
$162
This Orbitz deal was found by Cheapflights users on 4/4. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Orbitz is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 5/74:04 pm
ONT
- STL
1 stop26h 19m
Frontier
Sun 5/1012:36 pm
STL
- ONT
1 stop21h 13m
Frontier
Deal found 4/4![Frontier logo]()
$163
This CheapOair deal was found by Cheapflights users on 4/6. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure CheapOair is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 4/3011:47 am
ONT
- STL
1 stop7h 13m
Frontier
Fri 5/159:18 pm
STL
- ONT
1 stop24h 14m
Frontier
Deal found 4/6![Frontier logo]()
$171
This Booking.com deal was found by Cheapflights users on 4/5. Clicking the “Pick Dates” 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 4/3012:59 am
ONT
- STL
1 stop16h 22m
Frontier
Sun 5/39:55 pm
STL
- ONT
1 stop24h 09m
Frontier
Deal found 4/5![Frontier logo]()
$172
This Kiwi.com deal was found by Cheapflights users on 4/5. Clicking the “Pick Dates” 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 4/2412:59 am
ONT
- STL
1 stop16h 33m
Frontier
Thu 4/309:55 pm
STL
- ONT
2 stops11h 36m
Frontier
Deal found 4/5![Frontier logo]()
$175
This Kiwi.com deal was found by Cheapflights users on 4/3. 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 4/2912:59 am
ONT
- STL
1 stop16h 22m
Frontier
Wed 5/66:51 pm
STL
- ONT
2 stops17h 14m
Frontier
Deal found 4/3![Frontier logo]()
$177
This Frontier deal was found by Cheapflights users on 4/7. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 4/2311:47 am
ONT
- STL
1 stop7h 13m
Frontier
Thu 4/309:55 pm
STL
- ONT
1 stop12h 09m
Frontier
Deal found 4/7![Frontier logo]()
$180
This Trip.com deal was found by Cheapflights users on 4/3. 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.
Sun 4/268:21 am
ONT
- ORD
1 stop25h 56m
Frontier
Tue 4/288:58 pm
ORD
- ONT
1 stop15h 46m
Frontier
Deal found 4/3![Frontier logo]()
$253
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 8, 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 8, 2026.
This Delta deal was found by Cheapflights users on 4/4. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 4/2510:15 pm
ONT
- ORD
1 stop8h 22m
Delta
Sat 5/211:19 am
ORD
- ONT
1 stop9h 14m
Delta
Deal found 4/4![Delta logo]()
$262
This Southwest deal was found by Cheapflights users on 4/6. Clicking the “Pick Dates” 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 6/1011:55 pm
ONT
- MDW
Nonstop3h 45m
Southwest
Tue 6/165:25 am
MDW
- ONT
1 stop5h 50m
Southwest
Deal found 4/6![Southwest logo]()
$273
This United Airlines deal was found by Cheapflights users on 4/3. 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 United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 4/291:27 pm
ONT
- ORD
1 stop9h 32m
United Airlines
Wed 5/68:09 pm
ORD
- ONT
Nonstop4h 26m
United Airlines
Deal found 4/3![United Airlines logo]()
$330
This Kiwi.com deal was found by Cheapflights users on 4/4. Clicking the “Pick Dates” 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 5/144:04 pm
ONT
- STL
1 stop26h 19m
Frontier
Tue 5/196:51 pm
STL
- ONT
1 stop22h 53m
Frontier
Deal found 4/4![Frontier logo]()
$391
This American Airlines deal was found by Cheapflights users on 4/7. Clicking the “Pick Dates” 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 4/2812:19 pm
ONT
- MLI
2 stops9h 10m
American Airlines
Tue 5/1212:52 pm
MLI
- ONT
1 stop9h 35m
American Airlines
Deal found 4/7![American Airlines logo]()
$407
This Kiwi.com deal was found by Cheapflights users on 4/7. Clicking the “Pick Dates” 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 7/223:34 pm
ONT
- RFD
1 stop18h 50m
Multiple Airlines
Sun 7/261:14 pm
RFD
- ONT
1 stop27h 55m
Multiple Airlines
Deal found 4/7![Multiple Airlines logo]()
$412
This Alaska Airlines deal was found by Cheapflights users on 4/5. Clicking the “Pick Dates” 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 5/56:00 am
ONT
- STL
1 stop7h 50m
Alaska Airlines
Sat 5/97:00 am
STL
- ONT
1 stop9h 32m
Alaska Airlines
Deal found 4/5![Alaska Airlines logo]()
$413
This Delta deal was found by Cheapflights users on 4/3. 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 Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 5/286:00 am
ONT
- MDW
2 stops10h 33m
Delta
Thu 6/41:22 pm
MDW
- ONT
2 stops12h 12m
Delta
Deal found 4/3![Delta logo]()
$271
This Southwest deal was found by Cheapflights users on 4/7. Clicking the “Pick Dates” 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 5/111:55 pm
ONT
- MDW
Nonstop3h 45m
Southwest
Tue 5/54:00 pm
MDW
- ONT
2 stops8h 15m
Southwest
Deal found 4/7![Southwest logo]()
$329
This United Airlines deal was found by Cheapflights users on 4/4. Clicking the “Pick Dates” 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 5/201:40 pm
ONT
- ORD
1 stop8h 17m
United Airlines
Sat 5/238:13 pm
ORD
- ONT
Nonstop4h 33m
United Airlines
Deal found 4/4![United Airlines logo]()
$351
This Southwest deal was found by Cheapflights users on 4/6. Clicking the “Pick Dates” 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 5/111:55 pm
ONT
- MDW
Nonstop3h 45m
Southwest
Mon 5/410:05 am
MDW
- ONT
2 stops8h 20m
Southwest
Deal found 4/6![Southwest logo]()
$350
This United Airlines deal was found by Cheapflights users on 4/5. Clicking the “Pick Dates” 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
- ORD
1 stop8h 17m
United Airlines
Thu 5/76:20 am
ORD
- ONT
1 stop8h 02m
United Airlines
Deal found 4/5![United Airlines logo]()
$361
This American Airlines deal was found by Cheapflights users on 4/4. Clicking the “Pick Dates” 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 4/252:08 pm
ONT
- BMI
1 stop6h 19m
American Airlines
Sat 5/211:16 am
BMI
- ONT
2 stops10h 18m
American Airlines
Deal found 4/4![American Airlines logo]()
$434
This United Airlines deal was found by Cheapflights users on 4/3. 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 United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 5/27:00 am
ONT
- MLI
1 stop9h 00m
United Airlines
Mon 5/43:47 pm
MLI
- ONT
1 stop8h 48m
United Airlines
Deal found 4/3![United Airlines logo]()
$369
This Delta deal was found by Cheapflights users on 4/3. 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 Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 5/144:57 pm
ONT
- STL
1 stop5h 33m
Delta
Tue 5/197:59 pm
STL
- ONT
1 stop5h 35m
Delta
Deal found 4/3![Delta logo]()
$415
This Southwest deal was found by Cheapflights users on 4/7. Clicking the “Pick Dates” 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 6/104:35 pm
ONT
- MDW
1 stop5h 30m
Southwest
Sat 6/135:25 am
MDW
- ONT
1 stop5h 45m
Southwest
Deal found 4/7![Southwest logo]()
$385
This Alaska Airlines deal was found by Cheapflights users on 4/3. 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 Alaska Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 9/2312:10 pm
ONT
- STL
1 stop9h 49m
Alaska Airlines
Thu 9/243:12 pm
STL
- ONT
1 stop10h 12m
Alaska Airlines
Deal found 4/3![Alaska Airlines logo]()
$477
This Delta deal was found by Cheapflights users on 4/5. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 5/2510:00 pm
ONT
- ORD
2 stops13h 01m
Delta
Thu 6/45:19 pm
ORD
- ONT
2 stops8h 15m
Delta
Deal found 4/5![Delta logo]()
$416
This Kiwi.com deal was found by Cheapflights users on 4/4. Clicking the “Pick Dates” 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 8/2011:43 am
ONT
- RFD
1 stop7h 02m
Multiple Airlines
Sun 8/239:35 pm
RFD
- ONT
2 stops15h 23m
Multiple Airlines
Deal found 4/4![Multiple Airlines logo]()
$521
This Alaska Airlines deal was found by Cheapflights users on 4/4. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Alaska Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 9/2212:10 pm
ONT
- STL
1 stop9h 49m
Alaska Airlines
Sun 9/273:12 pm
STL
- ONT
1 stop10h 12m
Alaska Airlines
Deal found 4/4![Alaska Airlines logo]()
$477
This Southwest deal was found by Cheapflights users on 4/3. 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 Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 5/211:55 pm
ONT
- MDW
Nonstop3h 45m
Southwest
Sun 5/37:35 am
MDW
- ONT
2 stops9h 35m
Southwest
Deal found 4/3![Southwest logo]()
$397
This Delta deal was found by Cheapflights users on 4/6. Clicking the “Pick Dates” 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 5/236:00 am
ONT
- ORD
2 stops8h 51m
Delta
Tue 5/2612:47 pm
ORD
- ONT
1 stop11h 47m
Delta
Deal found 4/6![Delta logo]()
$425
This Alaska Airlines deal was found by Cheapflights users on 4/5. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Alaska Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 4/296:00 am
ONT
- STL
1 stop15h 59m
Alaska Airlines
Thu 4/304:46 pm
STL
- ONT
1 stop9h 13m
Alaska Airlines
Deal found 4/5![Alaska Airlines logo]()
$483
This United Airlines deal was found by Cheapflights users on 4/7. Clicking the “Pick Dates” 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 4/287:00 am
ONT
- MLI
1 stop8h 06m
United Airlines
Tue 5/123:47 pm
MLI
- ONT
1 stop8h 48m
United Airlines
Deal found 4/7![United Airlines logo]()
$441
This American Airlines deal was found by Cheapflights users on 4/8. Clicking the “Pick Dates” 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
- BMI
2 stops9h 33m
American Airlines
Sun 5/175:00 am
BMI
- ONT
2 stops8h 34m
American Airlines
Deal found 4/8![American Airlines logo]()
$535
This Southwest deal was found by Cheapflights users on 4/5. Clicking the “Pick Dates” 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 4/235:30 am
ONT
- MDW
1 stop5h 40m
Southwest
Wed 5/611:00 am
MDW
- ONT
Nonstop4h 15m
Southwest
Deal found 4/5![Southwest logo]()
$419
This Delta deal was found by Cheapflights users on 4/4. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 4/2512:49 pm
ONT
- BMI
1 stop7h 32m
Delta
Sat 5/212:02 pm
BMI
- ONT
1 stop8h 31m
Delta
Deal found 4/4![Delta logo]()
$429
This American Airlines deal was found by Cheapflights users on 4/3. 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.
Sun 5/312:18 pm
ONT
- BMI
1 stop6h 50m
American Airlines
Sat 6/64:22 pm
BMI
- ONT
1 stop8h 16m
American Airlines
Deal found 4/3![American Airlines logo]()
$545
This Southwest deal was found by Cheapflights users on 4/3. 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 Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 5/1412:50 pm
ONT
- STL
1 stop9h 00m
Southwest
Tue 5/194:25 pm
STL
- ONT
1 stop8h 00m
Southwest
Deal found 4/3![Southwest logo]()
$420
This United Airlines deal was found by Cheapflights users on 4/5. Clicking the “Pick Dates” 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 5/57:00 am
ONT
- PAH
1 stop9h 19m
United Airlines
Sat 5/95:00 am
PAH
- ONT
2 stops14h 52m
United Airlines
Deal found 4/5![United Airlines logo]()
$464
Last-minute flights from Ontario to IllinoisDiscover last-minute flight deals from Ontario to Illinois. Data last updated April 8, 2026 and is based on user searches.
Discover last-minute flight deals from Ontario to Illinois. Data last updated April 8, 2026 and is based on user searches.
This Frontier deal was found by Cheapflights users on 4/7. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 4/2311:47 am
ONT
- STL
1 stop7h 13m
Frontier
Thu 4/309:55 pm
STL
- ONT
1 stop12h 09m
Frontier
Deal found 4/7![Frontier logo]()
$180
This Kiwi.com deal was found by Cheapflights users on 4/5. Clicking the “Pick Dates” 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 4/2412:59 am
ONT
- STL
1 stop16h 33m
Frontier
Mon 4/278:17 pm
STL
- ONT
1 stop29h 38m
Frontier
Deal found 4/5![Frontier logo]()
$137
This Frontier deal was found by Cheapflights users on 4/3. 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 Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 4/245:33 pm
ONT
- STL
1 stop23h 59m
Frontier
Sat 5/28:17 pm
STL
- ONT
1 stop13h 09m
Frontier
Deal found 4/3![Frontier logo]()
$160
This Kiwi.com deal was found by Cheapflights users on 4/5. Clicking the “Pick Dates” 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 4/2412:59 am
ONT
- STL
1 stop16h 33m
Frontier
Thu 4/309:55 pm
STL
- ONT
2 stops11h 36m
Frontier
Deal found 4/5![Frontier logo]()
$175
This Trip.com deal was found by Cheapflights users on 4/3. 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.
Sun 4/268:21 am
ONT
- ORD
1 stop25h 56m
Frontier
Tue 4/288:58 pm
ORD
- ONT
1 stop15h 46m
Frontier
Deal found 4/3![Frontier logo]()
$253
This Kiwi.com deal was found by Cheapflights users on 4/3. 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 4/2912:59 am
ONT
- STL
1 stop16h 22m
Frontier
Wed 5/66:51 pm
STL
- ONT
2 stops17h 14m
Frontier
Deal found 4/3![Frontier logo]()
$177
This CheapOair deal was found by Cheapflights users on 4/6. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure CheapOair is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 4/3011:47 am
ONT
- STL
1 stop7h 13m
Frontier
Fri 5/159:18 pm
STL
- ONT
1 stop24h 14m
Frontier
Deal found 4/6![Frontier logo]()
$171
This Kiwi.com deal was found by Cheapflights users on 4/7. Clicking the “Pick Dates” 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 5/15:33 pm
ONT
- STL
1 stop23h 59m
Frontier
Mon 5/48:17 pm
STL
- ONT
1 stop15h 48m
Frontier
Deal found 4/7![Frontier logo]()
$135
This Trip.com deal was found by Cheapflights users on 4/6. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Trip.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 5/112:59 am
ONT
- STL
1 stop16h 33m
Frontier
Thu 5/712:36 pm
STL
- ONT
1 stop8h 56m
Frontier
Deal found 4/6![Frontier logo]()
$157
This Delta deal was found by Cheapflights users on 4/3. 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 Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 5/212:49 pm
ONT
- MDW
1 stop7h 39m
Delta
Tue 5/51:24 pm
MDW
- ONT
2 stops9h 36m
Delta
Deal found 4/3![Delta logo]()
$254
This Booking.com deal was found by Cheapflights users on 4/6. Clicking the “Pick Dates” 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 5/54:39 pm
ONT
- STL
1 stop23h 27m
Frontier
Fri 5/89:18 pm
STL
- ONT
1 stop19h 51m
Frontier
Deal found 4/6![Frontier logo]()
$162
This Orbitz deal was found by Cheapflights users on 4/4. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Orbitz is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 5/74:04 pm
ONT
- STL
1 stop26h 19m
Frontier
Sun 5/1012:36 pm
STL
- ONT
1 stop21h 13m
Frontier
Deal found 4/4![Frontier logo]()
$163
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 8, 2026.
Search for one-way flight options from Ontario to Illinois. Find affordable one-way fares based on user searches. Data last updated April 8, 2026.
This Trip.com deal was found by Cheapflights users on 4/8. Clicking the “Pick Dates” 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.
Sun 5/312:59 am
ONT
- STL
1 stop16h 33m
Frontier
Deal found 4/8![Frontier logo]()
$67
This Trip.com deal was found by Cheapflights users on 4/3. 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.
Wed 4/2912:59 am
ONT
- STL
1 stop16h 22m
Frontier
Deal found 4/3![Frontier logo]()
$68
This Kiwi.com deal was found by Cheapflights users on 4/5. Clicking the “Pick Dates” 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 5/910:50 am
ONT
- STL
1 stop6h 33m
Frontier
Deal found 4/5![Frontier logo]()
$69
This Kiwi.com deal was found by Cheapflights users on 4/4. Clicking the “Pick Dates” 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 5/128:06 pm
ONT
- ORD
1 stop24h 55m
Frontier
Deal found 4/4![Frontier logo]()
$70
This Trip.com deal was found by Cheapflights users on 4/5. Clicking the “Pick Dates” 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 5/68:06 pm
ONT
- ORD
1 stop24h 55m
Frontier
Deal found 4/5![Frontier logo]()
$72
This Super.com deal was found by Cheapflights users on 4/3. 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 Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 5/27:44 pm
ONT
- ORD
1 stop8h 24m
Frontier
Deal found 4/3![Frontier logo]()
$79
This Frontier deal was found by Cheapflights users on 4/6. Clicking the “Pick Dates” 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.
Sat 5/212:59 am
ONT
- ORD
1 stop6h 46m
Frontier
Deal found 4/6![Frontier logo]()
$80
This Trip.com deal was found by Cheapflights users on 4/7. Clicking the “Pick Dates” 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 5/58:06 pm
ONT
- ORD
1 stop24h 55m
Frontier
Deal found 4/7![Frontier logo]()
$81
This Trip.com deal was found by Cheapflights users on 4/7. Clicking the “Pick Dates” 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 5/188:06 pm
ONT
- ORD
1 stop24h 55m
Frontier
Deal found 4/7![Frontier logo]()
$82
This Super.com deal was found by Cheapflights users on 4/3. 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 Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 5/158:06 pm
ONT
- ORD
1 stop24h 55m
Frontier
Deal found 4/3![Frontier logo]()
$84
This Super.com deal was found by Cheapflights users on 4/4. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 5/216:00 am
ONT
- STL
1 stop11h 23m
Frontier
Deal found 4/4![Frontier logo]()
$85
This Super.com deal was found by Cheapflights users on 4/3. 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 Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 4/278:26 am
ONT
- ORD
1 stop28h 51m
Frontier
Deal found 4/3![Frontier logo]()
$85
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 8, 2026.
Most accurate provider | FlightHub 3 stars |
|---|---|
Most trusted provider | FlightHub 3 stars |
Round-trip from | $135 (Kiwi.com) |
One-way from | $67 (Trip.com) |
Popular in | February |
Cheapest in | September |
Average price | $313 |
Good round-trip deal | $391 or less |
Good one-way deal | $228 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 8, 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
OntarioChicago
ONT - ORD
ONTORD
Ontario
Sat 4/25
10:15 pm-8:37 am
1 stop8h 22m
Chicago O'Hare Intl
Sat 5/2
11:19 am-6:33 pm
1 stop9h 14m
$262
OntarioChicago
ONT - MDW
ONTMDW
Ontario
Thu 5/28
6:00 am-6:33 pm
2 stops10h 33m
Chicago Midway
Thu 6/4
1:22 pm-11:34 pm
2 stops12h 12m
$271
Quickest round-trip
OntarioChicago
ONT - MDW
ONTMDW
Ontario
Wed 6/10
11:55 pm-5:40 am
Nonstop3h 45m
Chicago Midway
Tue 6/16
5:25 am-9:15 am
1 stop5h 50m
$273
OntarioChicago
ONT - MDW
ONTMDW
Ontario
Fri 5/1
11:55 pm-5:40 am
Nonstop3h 45m
Chicago Midway
Tue 5/5
4:00 pm-10:15 pm
2 stops8h 15m
$329
OntarioChicago
ONT - ORD
ONTORD
Ontario
Wed 4/29
1:27 pm-12:59 am
1 stop9h 32m
Chicago O'Hare Intl
Wed 5/6
8:09 pm-10:35 pm
Nonstop4h 26m
$330
OntarioChicago
ONT - MDW
ONTMDW
Ontario
Fri 5/1
11:55 pm-5:40 am
Nonstop3h 45m
Chicago Midway
Mon 5/4
10:05 am-4:25 pm
2 stops8h 20m
$350
OntarioChicago
ONT - ORD
ONTORD
Ontario
Wed 5/20
1:40 pm-11:57 pm
1 stop8h 17m
Chicago O'Hare Intl
Sat 5/23
8:13 pm-10:46 pm
Nonstop4h 33m
$351
OntarioChicago
ONT - ORD
ONTORD
Ontario
Wed 5/6
1:40 pm-11:57 pm
1 stop8h 17m
Chicago O'Hare Intl
Thu 5/7
6:20 am-12:22 pm
1 stop8h 02m
$361
OntarioMoline
ONT - MLI
ONTMLI
Ontario
Sat 5/2
7:00 am-6:00 pm
1 stop9h 00m
Moline Quad-City
Mon 5/4
3:47 pm-10:35 pm
1 stop8h 48m
$369
OntarioChicago
ONT - MDW
ONTMDW
Ontario
Wed 6/10
4:35 pm-12:05 am
1 stop5h 30m
Chicago Midway
Sat 6/13
5:25 am-9:10 am
1 stop5h 45m
$385
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-MLI
ONT-MDW
ONT-RFD
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-MLI
ONT-MDW
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 $94). Flying from Ontario to Illinois in February is currently the most expensive (average of $198). 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 8, 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 8, 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.
Crew
8.6
Entertainment
7.5
Food
7.0
Boarding
8.1
Comfort
8.0
Overall
8.0
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Crew
8.6
Entertainment
7.5
Food
7.0
Boarding
8.1
Comfort
8.0
Overall
8.0
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Crew
8.6
Entertainment
7.5
Food
7.0
Boarding
8.1
Comfort
8.0
Overall
8.0
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Crew
8.6
Entertainment
7.5
Food
7.0
Boarding
8.1
Comfort
8.0
Overall
8.0
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Crew
8.6
Entertainment
7.5
Food
7.0
Boarding
8.1
Comfort
8.0
Overall
8.0
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Crew
8.6
Entertainment
7.5
Food
7.0
Boarding
8.1
Comfort
8.0
Overall
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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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 8, 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 8, 2026.
| Airline | Cheapest | Average | Flexibility | On-time |
|---|---|---|---|---|
| Cheapest$98 | Average$241 | FlexibilityNo cancel fee | On-time62% | |
| Cheapest$226 | Average$463 | FlexibilityNo cancel fee | On-time69% | |
| Cheapest$237 | Average$370 | FlexibilityNo cancel fee | On-time63% | |
| Cheapest$256 | Average$416 | FlexibilityNo cancel fee | On-timeN/A | |
| Cheapest$288 | Average$528 | FlexibilityNo cancel fee | On-time71% |