$72+ Cheap flights from Ontario (ONT) to Illinois
This is the cheapest one-way flight price found by a Cheapflights user in the last 72 hours by searching for a flight departing on 5/12. Fares are subject to change and may not be available on all flights or dates of travel.
ONT — ORD
Apr 6 — Apr 131
Round-trip
1 adult, Economy
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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 March 7, 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 March 7, 2026.
This Kiwi.com deal was found by Cheapflights users on 3/3. 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 5/612:59 am
ONT
- STL
1 stop16h 13m
Frontier
Mon 5/118:12 pm
STL
- ONT
1 stop29h 43m
Frontier
Deal found 3/3![Frontier logo]()
$155
This Kiwi.com deal was found by Cheapflights users on 3/3. 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.
Fri 4/245:33 pm
ONT
- STL
1 stop23h 59m
Frontier
Mon 4/278:17 pm
STL
- ONT
1 stop29h 38m
Frontier
Deal found 3/3![Frontier logo]()
$157
This Kiwi.com deal was found by Cheapflights users on 3/4. 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.
Wed 5/612:59 am
ONT
- STL
1 stop16h 13m
Frontier
Sat 5/98:12 pm
STL
- ONT
1 stop13h 19m
Frontier
Deal found 3/4![Frontier logo]()
$159
This Trip.com deal was found by Cheapflights users on 3/4. 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 Trip.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 4/279:55 pm
STL
- ONT
1 stop14h 49m
Frontier
Deal found 3/4![Frontier logo]()
$165
This Trip.com deal was found by Cheapflights users on 3/2. 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 Trip.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
Sun 4/269:55 pm
STL
- ONT
1 stop12h 29m
Frontier
Deal found 3/2![Frontier logo]()
$183
This Frontier deal was found by Cheapflights users on 3/4. 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 Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 4/910:27 pm
ONT
- STL
1 stop11h 00m
Frontier
Sat 4/188:17 pm
STL
- ONT
1 stop13h 09m
Frontier
Deal found 3/4![Frontier logo]()
$189
This Expedia deal was found by Cheapflights users on 3/3. 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.
Fri 4/1711:44 am
ONT
- STL
1 stop25h 37m
Frontier
Sun 4/199:55 pm
STL
- ONT
1 stop14h 19m
Frontier
Deal found 3/3![Frontier logo]()
$190
This Booking.com deal was found by Cheapflights users on 3/2. 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 4/249:59 pm
ONT
- STL
1 stop15h 22m
Frontier
Sat 4/258:17 pm
STL
- ONT
1 stop13h 09m
Frontier
Deal found 3/2![Frontier logo]()
$192
This Mytrip deal was found by Cheapflights users on 3/6. 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 Mytrip is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 3/242:23 pm
ONT
- STL
1 stop18h 56m
Frontier
Wed 3/258:12 pm
STL
- ONT
1 stop5h 47m
Frontier
Deal found 3/6![Frontier logo]()
$196
This Booking.com deal was found by Cheapflights users on 3/4. 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 Booking.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 4/1611:47 am
ONT
- STL
1 stop7h 13m
Frontier
Sun 4/199:55 pm
STL
- ONT
1 stop14h 19m
Frontier
Deal found 3/4![Frontier logo]()
$197
This Kiwi.com deal was found by Cheapflights users on 3/7. 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.
Sat 4/187:44 pm
ONT
- ORD
1 stop7h 41m
Multiple Airlines
Fri 4/2410:07 pm
ORD
- ONT
1 stop14h 37m
Multiple Airlines
Deal found 3/7![Multiple Airlines logo]()
$216
This Kiwi.com deal was found by Cheapflights users on 3/5. 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.
Thu 4/1612:59 am
ONT
- ORD
1 stop6h 51m
Frontier
Tue 4/213:27 pm
ORD
- ONT
2 stops34h 28m
Frontier
Deal found 3/5![Frontier logo]()
$217
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 March 7, 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 March 7, 2026.
This Delta deal was found by Cheapflights users on 3/6. 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.
Tue 4/76:00 am
ONT
- STL
1 stop5h 17m
Delta
Thu 4/96:12 pm
STL
- ONT
1 stop7h 39m
Delta
Deal found 3/6![Delta logo]()
$313
This United Airlines deal was found by Cheapflights users on 3/7. 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.
Wed 4/81:34 pm
ONT
- MLI
1 stop5h 58m
United Airlines
Wed 4/153:20 pm
MLI
- ONT
1 stop9h 11m
United Airlines
Deal found 3/7![United Airlines logo]()
$329
This Southwest deal was found by Cheapflights users on 3/3. 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.
Wed 3/252:20 pm
ONT
- STL
1 stop6h 20m
Southwest
Mon 3/305:20 pm
STL
- ONT
1 stop7h 25m
Southwest
Deal found 3/3![Southwest logo]()
$336
This Alaska Airlines deal was found by Cheapflights users on 3/7. 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 Alaska Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 5/125:56 pm
ONT
- ORD
1 stop9h 09m
Alaska Airlines
Tue 6/95:44 pm
ORD
- ONT
1 stop8h 14m
Alaska Airlines
Deal found 3/7![Alaska Airlines logo]()
$457
This American Airlines deal was found by Cheapflights users on 3/3. 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 4/102:08 pm
ONT
- BMI
1 stop6h 19m
American Airlines
Sun 4/123:45 pm
BMI
- ONT
1 stop8h 51m
American Airlines
Deal found 3/3![American Airlines logo]()
$546
This Kiwi.com deal was found by Cheapflights users on 3/5. 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 5/239:11 pm
ONT
- RFD
1 stop13h 10m
Multiple Airlines
Sun 5/311:11 pm
RFD
- ONT
1 stop9h 05m
Multiple Airlines
Deal found 3/5![Multiple Airlines logo]()
$581
This Delta deal was found by Cheapflights users on 3/3. 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.
Mon 4/65:09 pm
ONT
- STL
1 stop5h 12m
Delta
Tue 4/77:15 am
STL
- ONT
1 stop7h 08m
Delta
Deal found 3/3![Delta logo]()
$313
This United Airlines deal was found by Cheapflights users on 3/6. 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 United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 4/151:34 pm
ONT
- MLI
1 stop5h 58m
United Airlines
Wed 4/221:55 pm
MLI
- ONT
2 stops9h 55m
United Airlines
Deal found 3/6![United Airlines logo]()
$334
This Southwest deal was found by Cheapflights users on 3/3. 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.
Mon 4/2011:55 pm
ONT
- MDW
Nonstop3h 45m
Southwest
Wed 4/226:10 am
MDW
- ONT
1 stop7h 25m
Southwest
Deal found 3/3![Southwest logo]()
$342
This Delta deal was found by Cheapflights users on 3/6. 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 4/412:57 pm
ONT
- STL
1 stop9h 01m
Delta
Wed 4/86:12 pm
STL
- ONT
1 stop7h 39m
Delta
Deal found 3/6![Delta logo]()
$313
This United Airlines deal was found by Cheapflights users on 3/6. 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 United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 5/46:59 pm
ONT
- STL
1 stop8h 48m
United Airlines
Wed 5/68:46 am
STL
- ONT
1 stop5h 52m
United Airlines
Deal found 3/6![United Airlines logo]()
$348
This Southwest deal was found by Cheapflights users on 3/6. 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 4/153:45 pm
ONT
- MDW
1 stop5h 35m
Southwest
Tue 4/214:00 pm
MDW
- ONT
2 stops8h 10m
Southwest
Deal found 3/6![Southwest logo]()
$348
This Delta deal was found by Cheapflights users on 3/4. 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.
Wed 4/112:57 pm
ONT
- STL
1 stop9h 01m
Delta
Mon 4/66:12 pm
STL
- ONT
1 stop7h 39m
Delta
Deal found 3/4![Delta logo]()
$346
This United Airlines deal was found by Cheapflights users on 3/6. 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 United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 5/137:00 am
ONT
- ORD
Nonstop4h 03m
United Airlines
Fri 5/158:09 pm
ORD
- ONT
Nonstop4h 26m
United Airlines
Deal found 3/6![United Airlines logo]()
$348
This Southwest deal was found by Cheapflights users on 3/3. 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.
Mon 4/1311:55 pm
ONT
- MDW
Nonstop3h 45m
Southwest
Wed 4/154:00 pm
MDW
- ONT
2 stops8h 10m
Southwest
Deal found 3/3![Southwest logo]()
$354
This United Airlines deal was found by Cheapflights users on 3/2. 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.
Fri 4/101:43 pm
ONT
- PIA
1 stop5h 36m
United Airlines
Sun 4/125:35 pm
PIA
- ONT
1 stop6h 56m
United Airlines
Deal found 3/2![United Airlines logo]()
$351
This Delta deal was found by Cheapflights users on 3/4. 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.
Wed 4/112:57 pm
ONT
- STL
1 stop9h 01m
Delta
Tue 4/76:29 am
STL
- ONT
2 stops19h 22m
Delta
Deal found 3/4![Delta logo]()
$363
This Southwest deal was found by Cheapflights users on 3/2. 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.
Mon 5/1111:55 pm
ONT
- MDW
Nonstop3h 45m
Southwest
Thu 5/2111:00 am
MDW
- ONT
Nonstop4h 15m
Southwest
Deal found 3/2![Southwest logo]()
$426
This Delta deal was found by Cheapflights users on 3/3. 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.
Sun 4/196:00 am
ONT
- STL
1 stop5h 23m
Delta
Wed 4/226:00 am
STL
- ONT
1 stop7h 36m
Delta
Deal found 3/3![Delta logo]()
$397
This United Airlines deal was found by Cheapflights users on 3/2. 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 3/311:34 pm
ONT
- STL
1 stop5h 20m
United Airlines
Tue 4/74:49 pm
STL
- ONT
1 stop7h 01m
United Airlines
Deal found 3/2![United Airlines logo]()
$403
This Southwest deal was found by Cheapflights users on 3/3. 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.
Fri 4/1711:55 pm
ONT
- MDW
Nonstop3h 45m
Southwest
Sun 4/199:50 pm
MDW
- ONT
Nonstop4h 20m
Southwest
Deal found 3/3![Southwest logo]()
$433
This Delta deal was found by Cheapflights users on 3/7. 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 Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 4/157:05 am
ONT
- MLI
1 stop7h 23m
Delta
Wed 4/225:55 am
MLI
- ONT
1 stop7h 41m
Delta
Deal found 3/7![Delta logo]()
$399
This United Airlines deal was found by Cheapflights users on 3/2. 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 4/286:05 am
ONT
- PIA
2 stops13h 08m
United Airlines
Sat 5/21:35 pm
PIA
- ONT
1 stop6h 26m
United Airlines
Deal found 3/2![United Airlines logo]()
$404
This Delta deal was found by Cheapflights users on 3/4. 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.
Sun 4/55:09 pm
ONT
- STL
1 stop5h 12m
Delta
Mon 4/66:12 pm
STL
- ONT
2 stops30h 22m
Delta
Deal found 3/4![Delta logo]()
$399
This Southwest deal was found by Cheapflights users on 3/4. 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 Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 4/1011:55 pm
ONT
- MDW
Nonstop3h 45m
Southwest
Sun 4/129:50 pm
MDW
- ONT
Nonstop4h 20m
Southwest
Deal found 3/4![Southwest logo]()
$443
This United Airlines deal was found by Cheapflights users on 3/5. 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 4/11:34 pm
ONT
- STL
1 stop5h 20m
United Airlines
Tue 4/78:54 am
STL
- ONT
2 stops11h 08m
United Airlines
Deal found 3/5![United Airlines logo]()
$408
This American Airlines deal was found by Cheapflights users on 3/7. 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.
Thu 4/236:00 am
ONT
- BMI
1 stop7h 15m
American Airlines
Sun 4/265:00 am
BMI
- ONT
2 stops8h 34m
American Airlines
Deal found 3/7![American Airlines logo]()
$764
This Southwest deal was found by Cheapflights users on 3/4. 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 Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sun 4/59:25 pm
ONT
- MDW
1 stop5h 55m
Southwest
Wed 4/84:00 pm
MDW
- ONT
2 stops8h 10m
Southwest
Deal found 3/4![Southwest logo]()
$449
This United Airlines deal was found by Cheapflights users on 3/3. 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.
Mon 4/201:34 pm
ONT
- ORD
1 stop8h 55m
United Airlines
Wed 4/228:05 pm
ORD
- ONT
Nonstop4h 26m
United Airlines
Deal found 3/3![United Airlines logo]()
$416
This American Airlines deal was found by Cheapflights users on 3/5. 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 American Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 3/206:00 am
ONT
- SPI
2 stops10h 03m
American Airlines
Tue 3/245:00 am
SPI
- ONT
2 stops13h 22m
American Airlines
Deal found 3/5![American Airlines logo]()
$772
Last-minute flights from Ontario to IllinoisDiscover last-minute flight deals from Ontario to Illinois. Data last updated March 7, 2026 and is based on user searches.
Discover last-minute flight deals from Ontario to Illinois. Data last updated March 7, 2026 and is based on user searches.
This Mytrip deal was found by Cheapflights users on 3/6. 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 Mytrip is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 3/242:23 pm
ONT
- STL
1 stop18h 56m
Frontier
Wed 3/258:12 pm
STL
- ONT
1 stop5h 47m
Frontier
Deal found 3/6![Frontier logo]()
$196
This Frontier deal was found by Cheapflights users on 3/3. 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.
Thu 4/210:50 am
ONT
- STL
1 stop8h 27m
Frontier
Wed 4/88:16 pm
STL
- ONT
1 stop5h 40m
Frontier
Deal found 3/3![Frontier logo]()
$214
This Frontier deal was found by Cheapflights users on 3/4. 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 Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 4/910:27 pm
ONT
- STL
1 stop11h 00m
Frontier
Sat 4/188:17 pm
STL
- ONT
1 stop13h 09m
Frontier
Deal found 3/4![Frontier logo]()
$189
This Booking.com deal was found by Cheapflights users on 3/4. 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 Booking.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 4/1611:47 am
ONT
- STL
1 stop7h 13m
Frontier
Sun 4/199:55 pm
STL
- ONT
1 stop14h 19m
Frontier
Deal found 3/4![Frontier logo]()
$197
This Expedia deal was found by Cheapflights users on 3/3. 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.
Fri 4/1711:44 am
ONT
- STL
1 stop25h 37m
Frontier
Sun 4/199:55 pm
STL
- ONT
1 stop14h 19m
Frontier
Deal found 3/3![Frontier logo]()
$190
This Kiwi.com deal was found by Cheapflights users on 3/7. 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.
Sat 4/187:44 pm
ONT
- ORD
1 stop7h 41m
Multiple Airlines
Fri 4/2410:07 pm
ORD
- ONT
1 stop14h 37m
Multiple Airlines
Deal found 3/7![Multiple Airlines logo]()
$216
This Booking.com deal was found by Cheapflights users on 3/3. 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.
Sun 4/1912:59 am
ONT
- STL
1 stop16h 33m
Frontier
Sat 4/258:17 pm
STL
- ONT
1 stop13h 09m
Frontier
Deal found 3/3![Frontier logo]()
$203
This Kiwi.com deal was found by Cheapflights users on 3/3. 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.
Fri 4/245:33 pm
ONT
- STL
1 stop23h 59m
Frontier
Mon 4/278:17 pm
STL
- ONT
1 stop29h 38m
Frontier
Deal found 3/3![Frontier logo]()
$157
This Trip.com deal was found by Cheapflights users on 3/4. 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 Trip.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 4/279:55 pm
STL
- ONT
1 stop14h 49m
Frontier
Deal found 3/4![Frontier logo]()
$165
This Trip.com deal was found by Cheapflights users on 3/2. 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 Trip.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
Sun 4/269:55 pm
STL
- ONT
1 stop12h 29m
Frontier
Deal found 3/2![Frontier logo]()
$183
This Booking.com deal was found by Cheapflights users on 3/2. 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 4/249:59 pm
ONT
- STL
1 stop15h 22m
Frontier
Sat 4/258:17 pm
STL
- ONT
1 stop13h 09m
Frontier
Deal found 3/2![Frontier logo]()
$192
This Gotogate deal was found by Cheapflights users on 3/5. 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 Gotogate 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 4/308:06 pm
STL
- ONT
1 stop5h 49m
Frontier
Deal found 3/5![Frontier logo]()
$217
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 March 7, 2026.
Search for one-way flight options from Ontario to Illinois. Find affordable one-way fares based on user searches. Data last updated March 7, 2026.
This Trip.com deal was found by Cheapflights users on 3/6. 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.
Tue 5/127:29 pm
ONT
- ORD
1 stop9h 18m
Frontier
Deal found 3/6![Frontier logo]()
$72
This Kiwi.com deal was found by Cheapflights users on 3/4. 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.
Wed 4/157:44 pm
ONT
- ORD
1 stop7h 41m
Multiple Airlines
Deal found 3/4![Multiple Airlines logo]()
$76
This Trip.com deal was found by Cheapflights users on 3/6. 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.
Mon 4/139:02 pm
ONT
- ORD
1 stop7h 18m
Frontier
Deal found 3/6![Frontier logo]()
$77
This Kiwi.com deal was found by Cheapflights users on 3/3. 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 4/157:44 pm
ONT
- ORD
1 stop8h 24m
Frontier
Deal found 3/3![Frontier logo]()
$83
This Trip.com deal was found by Cheapflights users on 3/6. 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 4/178:59 pm
ONT
- ORD
1 stop7h 09m
Frontier
Deal found 3/6![Frontier logo]()
$84
This WAYA deal was found by Cheapflights users on 3/6. 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 WAYA is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 4/178:59 pm
ONT
- ORD
1 stop6h 26m
Multiple Airlines
Deal found 3/6![Multiple Airlines logo]()
$87
This Trip.com deal was found by Cheapflights users on 3/3. 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 5/612:59 am
ONT
- STL
1 stop16h 13m
Frontier
Deal found 3/3![Frontier logo]()
$89
This Trip.com deal was found by Cheapflights users on 3/5. 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.
Sun 5/1712:59 am
ONT
- ORD
1 stop6h 51m
Frontier
Deal found 3/5![Frontier logo]()
$89
This Trip.com deal was found by Cheapflights users on 3/3. 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 5/612:59 am
ONT
- ORD
1 stop6h 51m
Frontier
Deal found 3/3![Frontier logo]()
$90
This Kiwi.com deal was found by Cheapflights users on 3/3. 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.
Tue 4/147:44 pm
ONT
- ORD
1 stop8h 24m
Frontier
Deal found 3/3![Frontier logo]()
$91
This Kiwi.com deal was found by Cheapflights users on 3/4. 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.
Wed 4/2912:59 am
ONT
- STL
1 stop16h 22m
Frontier
Deal found 3/4![Frontier logo]()
$94
This Super.com deal was found by Cheapflights users on 3/3. 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 4/1812:59 am
ONT
- ORD
1 stop6h 46m
Frontier
Deal found 3/3![Frontier logo]()
$94
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 March 7, 2026.
Most accurate provider | FlightHub 3 stars |
|---|---|
Most trusted provider | FlightHub 3 stars |
Round-trip from | $155 (Kiwi.com) |
One-way from | $72 (Trip.com) |
Popular in | December |
Cheapest in | January |
Average price | $458 |
Good round-trip deal | $339 or less |
Good one-way deal | $189 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 March 7, 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
Tue 4/7
6:00 am-1:17 pm
1 stop5h 17m
Lambert-St Louis
Thu 4/9
6:12 pm-11:51 pm
1 stop7h 39m
$313
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
Mon 4/6
5:09 pm-12:21 am
1 stop5h 12m
Lambert-St Louis
Tue 4/7
7:15 am-12:23 pm
1 stop7h 08m
$313
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
Sat 4/4
12:57 pm-11:58 pm
1 stop9h 01m
Lambert-St Louis
Wed 4/8
6:12 pm-11:51 pm
1 stop7h 39m
$313
OntarioMoline
ONT - MLI
ONTMLI
Ontario
Wed 4/8
1:34 pm-9:32 pm
1 stop5h 58m
Moline Quad-City
Wed 4/15
3:20 pm-10:31 pm
1 stop9h 11m
$329
OntarioMoline
ONT - MLI
ONTMLI
Ontario
Wed 4/15
1:34 pm-9:32 pm
1 stop5h 58m
Moline Quad-City
Wed 4/22
1:55 pm-9:50 pm
2 stops9h 55m
$334
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
Wed 3/25
2:20 pm-10:40 pm
1 stop6h 20m
Lambert-St Louis
Mon 3/30
5:20 pm-10:45 pm
1 stop7h 25m
$336
OntarioChicago
ONT - MDW
ONTMDW
Ontario
Mon 4/20
11:55 pm-5:40 am
Nonstop3h 45m
Chicago Midway
Wed 4/22
6:10 am-11:35 am
1 stop7h 25m
$342
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
Wed 4/1
12:57 pm-11:58 pm
1 stop9h 01m
Lambert-St Louis
Mon 4/6
6:12 pm-11:51 pm
1 stop7h 39m
$346
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
Mon 5/4
6:59 pm-5:47 am
1 stop8h 48m
Lambert-St Louis
Wed 5/6
8:46 am-12:38 pm
1 stop5h 52m
$348
OntarioChicago
ONT - MDW
ONTMDW
Ontario
Wed 4/15
3:45 pm-11:20 pm
1 stop5h 35m
Chicago Midway
Tue 4/21
4:00 pm-10:10 pm
2 stops8h 10m
$348
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-RFD
ONT-STL
ONT-ORD
ONT-MDW
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-RFD
ONT-STL
ONT-ORD
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 $93). Flying from Ontario to Illinois in February is currently the most expensive (average of $236). 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 March 7, 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.
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 March 7, 2026.
Read through reviews of airlines operating flights from Ontario to Illinois, such as Southwest, Delta, and United Airlines. You can also see how each airline stacks up in terms of entertainment options, comfort, food, crew/service, and boarding process.
Food
7.0
Crew
8.6
Entertainment
7.5
Overall
8.0
Comfort
8.0
Boarding
8.1
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Food
7.0
Crew
8.6
Entertainment
7.5
Overall
8.0
Comfort
8.0
Boarding
8.1
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Food
7.0
Crew
8.6
Entertainment
7.5
Overall
8.0
Comfort
8.0
Boarding
8.1
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Food
7.0
Crew
8.6
Entertainment
7.5
Overall
8.0
Comfort
8.0
Boarding
8.1
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Food
7.0
Crew
8.6
Entertainment
7.5
Overall
8.0
Comfort
8.0
Boarding
8.1
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Food
7.0
Crew
8.6
Entertainment
7.5
Overall
8.0
Comfort
8.0
Boarding
8.1
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 March 7, 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 March 7, 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$388 | FlexibilityNo cancel fee | On-time63% | |
| Cheapest$246 | Average$472 | FlexibilityNo cancel fee | On-time71% | |
| Cheapest$256 | Average$373 | FlexibilityNo cancel fee | On-timeN/A |