$79+ 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 4/15. Fares are subject to change and may not be available on all flights or dates of travel.
ONT — ORD
Apr 29 — May 61
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 March 30, 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 30, 2026.
This Expedia deal was found by Cheapflights users on 3/27. Clicking the “Pick Dates” 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 5/76:00 am
ONT
- STL
1 stop11h 23m
Frontier
Sat 5/99:18 pm
STL
- ONT
1 stop19h 51m
Frontier
Deal found 3/27![Frontier logo]()
$160
This Booking.com deal was found by Cheapflights users on 3/26. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Booking.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 5/112:59 am
ONT
- STL
1 stop16h 33m
Frontier
Mon 5/49:55 pm
STL
- ONT
1 stop19h 49m
Frontier
Deal found 3/26![Frontier logo]()
$162
This Booking.com deal was found by Cheapflights users on 3/25. Clicking the “Pick Dates” 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 4/2311:47 am
ONT
- STL
1 stop7h 13m
Frontier
Sun 4/269:55 pm
STL
- ONT
1 stop12h 29m
Frontier
Deal found 3/25![Frontier logo]()
$167
This CheapOair deal was found by Cheapflights users on 3/27. Clicking the “Pick Dates” 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 5/64:39 pm
ONT
- STL
1 stop16h 42m
Frontier
Fri 5/89:18 pm
STL
- ONT
1 stop19h 51m
Frontier
Deal found 3/27![Frontier logo]()
$171
This Booking.com deal was found by Cheapflights users on 3/25. Clicking the “Pick Dates” 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 4/227:44 pm
ONT
- STL
1 stop23h 16m
Frontier
Mon 4/279:55 pm
STL
- ONT
1 stop14h 49m
Frontier
Deal found 3/25![Frontier logo]()
$172
This Frontier deal was found by Cheapflights users on 3/26. Clicking the “Pick Dates” 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 5/86:00 am
ONT
- STL
1 stop11h 23m
Frontier
Sat 5/98:08 pm
STL
- ONT
1 stop5h 41m
Frontier
Deal found 3/26![Frontier logo]()
$185
This Booking.com deal was found by Cheapflights users on 3/24. Clicking the “Pick Dates” 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 4/297:44 pm
ONT
- STL
1 stop23h 16m
Frontier
Mon 5/49:55 pm
STL
- ONT
1 stop23h 37m
Frontier
Deal found 3/24![Frontier logo]()
$187
This Booking.com deal was found by Cheapflights users on 3/25. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Booking.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 5/48:59 pm
ONT
- STL
1 stop19h 07m
Frontier
Thu 5/78:08 pm
STL
- ONT
1 stop5h 41m
Frontier
Deal found 3/25![Frontier logo]()
$192
This CheapOair deal was found by Cheapflights users on 3/28. 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 CheapOair is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 5/18:20 pm
ONT
- STL
1 stop17h 01m
Frontier
Mon 5/48:17 pm
STL
- ONT
1 stop15h 48m
Frontier
Deal found 3/28![Frontier logo]()
$196
This Expedia deal was found by Cheapflights users on 3/27. Clicking the “Pick Dates” 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 4/106:20 am
ONT
- STL
1 stop25h 28m
Frontier
Mon 4/1312:22 pm
STL
- ONT
1 stop9h 45m
Frontier
Deal found 3/27![Frontier logo]()
$200
This CheapOair deal was found by Cheapflights users on 3/27. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure CheapOair is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 4/106:20 am
ONT
- STL
1 stop25h 28m
Frontier
Sun 4/121:14 pm
STL
- ONT
1 stop20h 50m
Frontier
Deal found 3/27![Frontier logo]()
$205
This Booking.com deal was found by Cheapflights users on 3/25. Clicking the “Pick Dates” 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 4/910:27 pm
ONT
- STL
1 stop11h 00m
Frontier
Sun 4/121:14 pm
STL
- ONT
1 stop20h 50m
Frontier
Deal found 3/25![Frontier logo]()
$207
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 30, 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 30, 2026.
This Delta deal was found by Cheapflights users on 3/27. Clicking the “Pick Dates” 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 4/2312:49 pm
ONT
- MDW
1 stop7h 39m
Delta
Tue 4/286:00 am
MDW
- ONT
1 stop7h 36m
Delta
Deal found 3/27![Delta logo]()
$261
This United Airlines deal was found by Cheapflights users on 3/29. 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 6/11:18 pm
ONT
- ORD
1 stop8h 01m
United Airlines
Thu 6/48:13 pm
ORD
- ONT
Nonstop4h 33m
United Airlines
Deal found 3/29![United Airlines logo]()
$276
This Southwest deal was found by Cheapflights users on 3/29. 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 Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 6/18:45 pm
ONT
- MDW
1 stop7h 00m
Southwest
Thu 6/45:15 am
MDW
- ONT
2 stops8h 05m
Southwest
Deal found 3/29![Southwest logo]()
$309
This Kiwi.com deal was found by Cheapflights users on 3/27. Clicking the “Pick Dates” 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 5/2310:50 am
ONT
- RFD
2 stops19h 41m
Multiple Airlines
Sun 5/241:11 pm
RFD
- ONT
1 stop8h 21m
Multiple Airlines
Deal found 3/27![Multiple Airlines logo]()
$379
This American Airlines deal was found by Cheapflights users on 3/29. 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.
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 3/29![American Airlines logo]()
$429
This Southwest deal was found by Cheapflights users on 3/29. 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 Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 5/2011:55 pm
ONT
- MDW
Nonstop3h 45m
Southwest
Sat 5/235:10 am
MDW
- ONT
1 stop7h 55m
Southwest
Deal found 3/29![Southwest logo]()
$337
This United Airlines deal was found by Cheapflights users on 3/29. 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.
Sat 5/21:40 pm
ONT
- ORD
1 stop8h 17m
United Airlines
Sat 5/93:35 pm
ORD
- ONT
Nonstop4h 26m
United Airlines
Deal found 3/29![United Airlines logo]()
$350
This Delta deal was found by Cheapflights users on 3/26. Clicking the “Pick Dates” 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 4/286:00 am
ONT
- STL
1 stop5h 23m
Delta
Thu 4/307:00 am
STL
- ONT
1 stop7h 14m
Delta
Deal found 3/26![Delta logo]()
$369
This Southwest deal was found by Cheapflights users on 3/29. 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 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 5/510:05 am
MDW
- ONT
2 stops6h 50m
Southwest
Deal found 3/29![Southwest logo]()
$350
This United Airlines deal was found by Cheapflights users on 3/28. 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.
Thu 4/236:49 pm
ONT
- ORD
1 stop8h 38m
United Airlines
Thu 4/308:09 pm
ORD
- ONT
Nonstop4h 26m
United Airlines
Deal found 3/28![United Airlines logo]()
$351
This Kiwi.com deal was found by Cheapflights users on 3/29. 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.
Wed 5/134:39 pm
ONT
- RFD
1 stop17h 21m
Multiple Airlines
Sun 5/1712:50 pm
RFD
- ONT
1 stop8h 42m
Multiple Airlines
Deal found 3/29![Multiple Airlines logo]()
$390
This Delta deal was found by Cheapflights users on 3/25. Clicking the “Pick Dates” 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 5/1612:07 pm
ONT
- MDW
1 stop7h 02m
Delta
Tue 5/199:23 am
MDW
- ONT
2 stops8h 54m
Delta
Deal found 3/25![Delta logo]()
$392
This Kiwi.com deal was found by Cheapflights users on 3/26. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 6/103:34 pm
ONT
- RFD
1 stop18h 49m
Multiple Airlines
Sun 6/141:13 pm
RFD
- ONT
1 stop8h 35m
Multiple Airlines
Deal found 3/26![Multiple Airlines logo]()
$404
This Southwest deal was found by Cheapflights users on 3/25. Clicking the “Pick Dates” 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 4/1810:30 am
ONT
- ORD
2 stops9h 50m
Southwest
Tue 4/216:15 am
ORD
- ONT
2 stops10h 50m
Southwest
Deal found 3/25![Southwest logo]()
$406
This Delta deal was found by Cheapflights users on 3/26. Clicking the “Pick Dates” 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 3/26![Delta logo]()
$419
This Kiwi.com deal was found by Cheapflights users on 3/27. Clicking the “Pick Dates” 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 4/1112:38 pm
ONT
- RFD
2 stops19h 09m
Multiple Airlines
Sun 4/1212:50 pm
RFD
- ONT
1 stop21h 14m
Multiple Airlines
Deal found 3/27![Multiple Airlines logo]()
$434
This United Airlines deal was found by Cheapflights users on 3/25. Clicking the “Pick Dates” 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 4/276:49 pm
ONT
- STL
1 stop9h 01m
United Airlines
Tue 4/284:49 pm
STL
- ONT
1 stop7h 01m
United Airlines
Deal found 3/25![United Airlines logo]()
$437
This American Airlines deal was found by Cheapflights users on 3/27. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure American Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 6/2711:59 pm
ONT
- MLI
1 stop8h 40m
American Airlines
Sat 7/47:20 am
MLI
- ONT
1 stop6h 25m
American Airlines
Deal found 3/27![American Airlines logo]()
$534
This Southwest deal was found by Cheapflights users on 3/25. Clicking the “Pick Dates” 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 5/3011:55 pm
ONT
- MDW
Nonstop3h 45m
Southwest
Sat 6/65:10 pm
MDW
- ONT
1 stop7h 40m
Southwest
Deal found 3/25![Southwest logo]()
$416
This Delta deal was found by Cheapflights users on 3/26. Clicking the “Pick Dates” 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 4/2212:49 pm
ONT
- MDW
1 stop7h 39m
Delta
Mon 4/2712:52 pm
MDW
- ONT
1 stop10h 08m
Delta
Deal found 3/26![Delta logo]()
$424
This United Airlines deal was found by Cheapflights users on 3/25. Clicking the “Pick Dates” 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 4/187:00 am
ONT
- PAH
1 stop9h 19m
United Airlines
Wed 4/222:10 pm
PAH
- ONT
1 stop9h 40m
United Airlines
Deal found 3/25![United Airlines logo]()
$454
This American Airlines deal was found by Cheapflights users on 3/26. Clicking the “Pick Dates” 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
- EVV
1 stop7h 02m
American Airlines
Tue 4/144:03 pm
EVV
- ONT
1 stop6h 51m
American Airlines
Deal found 3/26![American Airlines logo]()
$568
This Delta deal was found by Cheapflights users on 3/26. Clicking the “Pick Dates” 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 5/3010:00 pm
ONT
- MDW
2 stops12h 42m
Delta
Sat 6/69:23 am
MDW
- ONT
2 stops8h 54m
Delta
Deal found 3/26![Delta logo]()
$435
This United Airlines deal was found by Cheapflights users on 3/25. Clicking the “Pick Dates” 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 4/221:34 pm
ONT
- STL
1 stop5h 20m
United Airlines
Wed 4/298:54 am
STL
- ONT
2 stops10h 53m
United Airlines
Deal found 3/25![United Airlines logo]()
$467
This Southwest deal was found by Cheapflights users on 3/24. Clicking the “Pick Dates” 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 9/221:50 pm
ONT
- STL
1 stop7h 50m
Southwest
Mon 9/288:25 am
STL
- ONT
1 stop5h 35m
Southwest
Deal found 3/24![Southwest logo]()
$472
This Kiwi.com deal was found by Cheapflights users on 3/26. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 6/34:39 pm
ONT
- RFD
1 stop17h 44m
Multiple Airlines
Sun 6/71:13 pm
RFD
- ONT
1 stop8h 19m
Multiple Airlines
Deal found 3/26![Multiple Airlines logo]()
$549
This United Airlines deal was found by Cheapflights users on 3/25. Clicking the “Pick Dates” 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 6/276:30 am
ONT
- MLI
1 stop6h 42m
United Airlines
Sat 7/43:52 pm
MLI
- ONT
1 stop8h 59m
United Airlines
Deal found 3/25![United Airlines logo]()
$469
This Southwest deal was found by Cheapflights users on 3/24. Clicking the “Pick Dates” 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 4/88:05 am
ONT
- STL
2 stops7h 50m
Southwest
Mon 4/203:50 pm
STL
- ONT
2 stops9h 15m
Southwest
Deal found 3/24![Southwest logo]()
$475
This Delta deal was found by Cheapflights users on 3/26. Clicking the “Pick Dates” 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 7/610:00 pm
ONT
- STL
1 stop8h 19m
Delta
Fri 7/103:40 pm
STL
- ONT
1 stop8h 04m
Delta
Deal found 3/26![Delta logo]()
$477
This American Airlines deal was found by Cheapflights users on 3/26. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure American Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 4/2011:59 pm
ONT
- SPI
2 stops12h 20m
American Airlines
Wed 4/225:45 am
SPI
- ONT
2 stops9h 33m
American Airlines
Deal found 3/26![American Airlines logo]()
$649
Last-minute flights from Ontario to IllinoisDiscover last-minute flight deals from Ontario to Illinois. Data last updated March 30, 2026 and is based on user searches.
Discover last-minute flight deals from Ontario to Illinois. Data last updated March 30, 2026 and is based on user searches.
This Expedia deal was found by Cheapflights users on 3/28. 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 Expedia is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 4/36:20 am
ONT
- STL
1 stop25h 28m
Frontier
Sun 5/39:55 pm
STL
- ONT
1 stop12h 09m
Frontier
Deal found 3/28![Frontier logo]()
$215
This Booking.com deal was found by Cheapflights users on 3/25. Clicking the “Pick Dates” 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 4/910:27 pm
ONT
- STL
1 stop11h 00m
Frontier
Sun 4/121:14 pm
STL
- ONT
1 stop20h 50m
Frontier
Deal found 3/25![Frontier logo]()
$207
This Travelocity deal was found by Cheapflights users on 3/27. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Travelocity is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 4/910:27 pm
ONT
- STL
1 stop11h 00m
Frontier
Mon 4/1312:22 pm
STL
- ONT
1 stop9h 45m
Frontier
Deal found 3/27![Frontier logo]()
$225
This Expedia deal was found by Cheapflights users on 3/27. Clicking the “Pick Dates” 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 4/106:20 am
ONT
- STL
1 stop25h 28m
Frontier
Mon 4/1312:22 pm
STL
- ONT
1 stop9h 45m
Frontier
Deal found 3/27![Frontier logo]()
$200
This CheapOair deal was found by Cheapflights users on 3/27. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure CheapOair is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 4/106:20 am
ONT
- STL
1 stop25h 28m
Frontier
Sun 4/121:14 pm
STL
- ONT
1 stop20h 50m
Frontier
Deal found 3/27![Frontier logo]()
$205
This Booking.com deal was found by Cheapflights users on 3/25. Clicking the “Pick Dates” 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 4/227:44 pm
ONT
- STL
1 stop23h 16m
Frontier
Mon 4/279:55 pm
STL
- ONT
1 stop14h 49m
Frontier
Deal found 3/25![Frontier logo]()
$172
This CheapOair deal was found by Cheapflights users on 3/28. 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 CheapOair is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 4/227:44 pm
ONT
- STL
1 stop23h 16m
Frontier
Wed 5/136:51 pm
STL
- ONT
1 stop22h 18m
Frontier
Deal found 3/28![Frontier logo]()
$216
This Booking.com deal was found by Cheapflights users on 3/25. Clicking the “Pick Dates” 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 4/2311:47 am
ONT
- STL
1 stop7h 13m
Frontier
Sun 4/269:55 pm
STL
- ONT
1 stop12h 29m
Frontier
Deal found 3/25![Frontier logo]()
$167
This CheapOair deal was found by Cheapflights users on 3/27. Clicking the “Pick Dates” 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 4/235:33 pm
ONT
- STL
1 stop23h 48m
Frontier
Mon 4/279:55 pm
STL
- ONT
1 stop22h 54m
Frontier
Deal found 3/27![Frontier logo]()
$196
This CheapOair deal was found by Cheapflights users on 3/26. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure CheapOair is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 4/249:59 pm
ONT
- STL
1 stop15h 22m
Frontier
Mon 4/279:55 pm
STL
- ONT
1 stop22h 54m
Frontier
Deal found 3/26![Frontier logo]()
$171
This Expedia deal was found by Cheapflights users on 3/28. 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 Expedia is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 4/2512:59 am
ONT
- STL
1 stop16h 22m
Frontier
Sun 5/39:55 pm
STL
- ONT
1 stop24h 09m
Frontier
Deal found 3/28![Frontier logo]()
$185
This Booking.com deal was found by Cheapflights users on 3/24. Clicking the “Pick Dates” 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 4/297:44 pm
ONT
- STL
1 stop23h 16m
Frontier
Mon 5/49:55 pm
STL
- ONT
1 stop23h 37m
Frontier
Deal found 3/24![Frontier logo]()
$187
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 30, 2026.
Search for one-way flight options from Ontario to Illinois. Find affordable one-way fares based on user searches. Data last updated March 30, 2026.
This Super.com deal was found by Cheapflights users on 3/25. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 4/1512:59 am
ONT
- ORD
1 stop6h 51m
Frontier
Deal found 3/25![Frontier logo]()
$79
This Trip.com deal was found by Cheapflights users on 3/27. Clicking the “Pick Dates” 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 4/147:44 pm
ONT
- ORD
1 stop8h 24m
Frontier
Deal found 3/27![Frontier logo]()
$82
This Kiwi.com deal was found by Cheapflights users on 3/25. Clicking the “Pick Dates” 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.
Mon 6/810:50 am
ONT
- ORD
1 stop7h 47m
Frontier
Deal found 3/25![Frontier logo]()
$83
This Super.com deal was found by Cheapflights users on 3/28. 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 Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 5/136:00 am
ONT
- ORD
1 stop12h 37m
Frontier
Deal found 3/28![Frontier logo]()
$85
This Frontier deal was found by Cheapflights users on 3/25. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 5/116:00 am
ONT
- STL
1 stop11h 23m
Frontier
Deal found 3/25![Frontier logo]()
$86
This Booking.com deal was found by Cheapflights users on 3/27. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Booking.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 5/158:06 pm
ONT
- ORD
1 stop24h 55m
Frontier
Deal found 3/27![Frontier logo]()
$87
This Trip.com deal was found by Cheapflights users on 3/24. Clicking the “Pick Dates” 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 3/24![Frontier logo]()
$89
This Trip.com deal was found by Cheapflights users on 3/26. Clicking the “Pick Dates” 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 4/1311:10 am
ONT
- ORD
1 stop17h 10m
Frontier
Deal found 3/26![Frontier logo]()
$90
This Trip.com deal was found by Cheapflights users on 3/28. 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 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
Deal found 3/28![Frontier logo]()
$91
This CheapOair deal was found by Cheapflights users on 3/26. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure CheapOair is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 4/1712:59 am
ONT
- STL
1 stop16h 33m
Frontier
Deal found 3/26![Frontier logo]()
$92
This Kiwi.com deal was found by Cheapflights users on 3/25. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 6/26:00 am
ONT
- STL
1 stop11h 23m
Frontier
Deal found 3/25![Frontier logo]()
$96
This Super.com deal was found by Cheapflights users on 3/28. 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 Super.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 3/28![Frontier logo]()
$99
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 30, 2026.
Most accurate provider | FlightHub 3 stars |
|---|---|
Most trusted provider | FlightHub 3 stars |
Round-trip from | $160 (Expedia) |
One-way from | $79 (Super.com) |
Popular in | February |
Cheapest in | September |
Average price | $351 |
Good round-trip deal | $363 or less |
Good one-way deal | $239 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 30, 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 - MDW
ONTMDW
Ontario
Thu 4/23
12:49 pm-10:28 pm
1 stop7h 39m
Chicago Midway
Tue 4/28
6:00 am-11:36 am
1 stop7h 36m
$261
OntarioChicago
ONT - ORD
ONTORD
Ontario
Mon 6/1
1:18 pm-11:19 pm
1 stop8h 01m
Chicago O'Hare Intl
Thu 6/4
8:13 pm-10:46 pm
Nonstop4h 33m
$276
OntarioChicago
ONT - MDW
ONTMDW
Ontario
Mon 6/1
8:45 pm-5:45 am
1 stop7h 00m
Chicago Midway
Thu 6/4
5:15 am-11:20 am
2 stops8h 05m
$309
OntarioChicago
ONT - MDW
ONTMDW
Ontario
Wed 5/20
11:55 pm-5:40 am
Nonstop3h 45m
Chicago Midway
Sat 5/23
5:10 am-11:05 am
1 stop7h 55m
$337
OntarioChicago
ONT - ORD
ONTORD
Ontario
Sat 5/2
1:40 pm-11:57 pm
1 stop8h 17m
Chicago O'Hare Intl
Sat 5/9
3:35 pm-6:01 pm
Nonstop4h 26m
$350
Quickest round-trip
OntarioChicago
ONT - MDW
ONTMDW
Ontario
Fri 5/1
11:55 pm-5:40 am
Nonstop3h 45m
Chicago Midway
Tue 5/5
10:05 am-2:55 pm
2 stops6h 50m
$350
OntarioChicago
ONT - ORD
ONTORD
Ontario
Thu 4/23
6:49 pm-5:27 am
1 stop8h 38m
Chicago O'Hare Intl
Thu 4/30
8:09 pm-10:35 pm
Nonstop4h 26m
$351
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
Tue 4/28
6:00 am-1:23 pm
1 stop5h 23m
Lambert-St Louis
Thu 4/30
7:00 am-12:14 pm
1 stop7h 14m
$369
OntarioChicago
ONT - RFD
ONTRFD
Ontario
Sat 5/23
10:50 am-8:31 am
2 stops19h 41m
Chicago Greater Rockford
Sun 5/24
1:11 pm-7:32 pm
1 stop8h 21m
$379
OntarioChicago
ONT - RFD
ONTRFD
Ontario
Wed 5/13
4:39 pm-12:00 pm
1 stop17h 21m
Chicago Greater Rockford
Sun 5/17
12:50 pm-7:32 pm
1 stop8h 42m
$390
Showing 1-10 of 60 resultsSorted by cheapest first
Best time to book a flight from Ontario to Illinois
Have a flexible travel schedule? Discover the best time to fly to Illinois from Ontario with our price prediction graph.
ONT-STL
ONT-MDW
ONT-RFD
ONT-ORD
ONT-SPI
Estimated round-trip price
Rates are based on past data. Find the cheapest month and day to book your flight based on your travel requirements, then search for cheap deals.
Cheapflights Insights
Everything you need to know about your flight from Ontario to Illinois
ONT-USIL
ONT-STL
ONT-MDW
ONT-RFD
ONT-ORD
What is the cheapest month to book a flight from Ontario to Illinois?
Currently, April is the cheapest month in which you can book a flight from Ontario to Illinois (average of $97). 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 March 30, 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 March 30, 2026.
Read through reviews of airlines operating flights from Ontario to Illinois, such as Southwest,Delta, andUnited Airlines. You can also see how each airline stacks up in terms of entertainment options, comfort, food, crew/service, and boarding process.
Food
7.0
Entertainment
7.5
Overall
8.0
Comfort
8.0
Boarding
8.1
Crew
8.6
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Food
7.0
Entertainment
7.5
Overall
8.0
Comfort
8.0
Boarding
8.1
Crew
8.6
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Food
7.0
Entertainment
7.5
Overall
8.0
Comfort
8.0
Boarding
8.1
Crew
8.6
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Food
7.0
Entertainment
7.5
Overall
8.0
Comfort
8.0
Boarding
8.1
Crew
8.6
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Food
7.0
Entertainment
7.5
Overall
8.0
Comfort
8.0
Boarding
8.1
Crew
8.6
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Food
7.0
Entertainment
7.5
Overall
8.0
Comfort
8.0
Boarding
8.1
Crew
8.6
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Related info for your journey
Find useful and relevant information for your journey from Ontario to Illinois. Access travel guides, tips, and recommendations to enhance your travel experience. Get information about local attractions, weather, transportation options, and more.
Browse thousands of different options on Cheapflights for your next trip
Toggle through the tabs below to find thousands of options on Cheapflights for your next trip.
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Alternative routes for Ontario to Illinois
See prices for flight routes from nearby airports that may be better suited for you.
Complete your trip
Complete your trip to Illinois by adding a car rental and/or hotel reservation to your travel itinerary.
Search flights from Ontario to Illinois by cabin class
Find flights from Ontario to Illinois, based on your preferred cabin class, be it economy, premium economy, business, or first class.
Ontario and Illinois flights
Browse other Ontario and Illinois flight options. Last updated on March 30, 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 30, 2026.
| Airline | Cheapest | Average | Flexibility | On-time |
|---|---|---|---|---|
| Cheapest$98 | Average$241 | FlexibilityNo cancel fee | On-time62% | |
| Cheapest$226 | Average$460 | FlexibilityNo cancel fee | On-time69% | |
| Cheapest$237 | Average$367 | FlexibilityNo cancel fee | On-time63% | |
| Cheapest$256 | Average$399 | FlexibilityNo cancel fee | On-timeN/A | |
| Cheapest$288 | Average$488 | FlexibilityNo cancel fee | On-time71% |