$93+ 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 5/13. Fares are subject to change and may not be available on all flights or dates of travel.
ONT — ORD
abr 17 — abr 241
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 março 18, 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 março 18, 2026.
This Frontier deal was found by Cheapflights users on 3/13. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
qui 4/1611:47 am
ONT
- STL
1 stop7h 13m
Frontier
qui 4/239:55 pm
STL
- ONT
1 stop12h 29m
Frontier
Deal found 3/13![Frontier logo]()
$210
This Booking.com deal was found by Cheapflights users on 3/16. Clicking the “Pick Dates” 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.
sex 4/1712:59 am
ONT
- STL
1 stop16h 33m
Frontier
sex 4/249:58 pm
STL
- ONT
1 stop22h 51m
Frontier
Deal found 3/16![Frontier logo]()
$212
This Frontier deal was found by Cheapflights users on 3/17. Clicking the “Pick Dates” 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.
sex 4/1712:59 am
ONT
- STL
1 stop16h 33m
Frontier
sáb 4/258:17 pm
STL
- ONT
1 stop13h 09m
Frontier
Deal found 3/17![Frontier logo]()
$213
This Gotogate deal was found by Cheapflights users on 3/15. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Gotogate is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
ter 4/76:20 am
ONT
- STL
1 stop25h 28m
Frontier
qua 4/88:16 pm
STL
- ONT
1 stop5h 40m
Frontier
Deal found 3/15![Frontier logo]()
$216
This Booking.com deal was found by Cheapflights users on 3/13. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Booking.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
qui 4/1611:47 am
ONT
- STL
1 stop7h 13m
Frontier
dom 4/199:55 pm
STL
- ONT
1 stop14h 19m
Frontier
Deal found 3/13![Frontier logo]()
$217
This Mytrip deal was found by Cheapflights users on 3/13. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Mytrip is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
sex 5/18:20 pm
ONT
- STL
1 stop17h 01m
Frontier
ter 5/56:51 pm
STL
- ONT
1 stop22h 53m
Frontier
Deal found 3/13![Frontier logo]()
$219
This CheapOair deal was found by Cheapflights users on 3/15. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure CheapOair is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
sex 5/15:33 pm
ONT
- STL
1 stop23h 59m
Frontier
dom 5/39:55 pm
STL
- ONT
1 stop12h 09m
Frontier
Deal found 3/15![Frontier logo]()
$221
This Kiwi.com deal was found by Cheapflights users on 3/13. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
sex 4/106:20 am
ONT
- STL
1 stop25h 28m
Frontier
seg 4/138:19 pm
STL
- ONT
1 stop29h 36m
Frontier
Deal found 3/13![Frontier logo]()
$224
This Frontier deal was found by Cheapflights users on 3/16. Clicking the “Pick Dates” 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.
qui 4/910:27 pm
ONT
- STL
1 stop11h 00m
Frontier
seg 4/1312:22 pm
STL
- ONT
1 stop9h 45m
Frontier
Deal found 3/16![Frontier logo]()
$230
This Frontier deal was found by Cheapflights users on 3/16. Clicking the “Pick Dates” 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.
qui 4/210:50 am
ONT
- STL
1 stop8h 27m
Frontier
qua 4/88:16 pm
STL
- ONT
1 stop5h 40m
Frontier
Deal found 3/16![Frontier logo]()
$240
This CheapOair deal was found by Cheapflights users on 3/16. Clicking the “Pick Dates” 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.
sex 4/106:20 am
ONT
- STL
1 stop25h 28m
Frontier
seg 5/119:18 pm
STL
- ONT
1 stop24h 14m
Frontier
Deal found 3/16![Frontier logo]()
$241
This Kiwi.com deal was found by Cheapflights users on 3/17. Clicking the “Pick Dates” 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.
sex 4/175:33 pm
ONT
- STL
1 stop23h 59m
Frontier
sex 4/249:58 pm
STL
- ONT
2 stops27h 57m
Frontier
Deal found 3/17![Frontier logo]()
$249
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 março 18, 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 março 18, 2026.
This Southwest deal was found by Cheapflights users on 3/17. Clicking the “Pick Dates” 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.
qui 4/1611:55 pm
ONT
- MDW
Nonstop3h 45m
Southwest
seg 4/2011:00 am
MDW
- ONT
Nonstop4h 15m
Southwest
Deal found 3/17![Southwest logo]()
$317
This Delta deal was found by Cheapflights users on 3/17. Clicking the “Pick Dates” 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.
ter 4/76:00 am
ONT
- STL
1 stop5h 17m
Delta
ter 4/76:12 pm
STL
- ONT
1 stop7h 39m
Delta
Deal found 3/17![Delta logo]()
$333
This American Airlines deal was found by Cheapflights users on 3/15. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure American Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
qua 4/1512:19 pm
ONT
- MLI
2 stops9h 35m
American Airlines
qua 4/2212:52 pm
MLI
- ONT
1 stop10h 15m
American Airlines
Deal found 3/15![American Airlines logo]()
$354
This United Airlines deal was found by Cheapflights users on 3/17. Clicking the “Pick Dates” 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.
qua 6/36:30 am
ONT
- ORD
Nonstop4h 15m
United Airlines
qua 6/108:13 pm
ORD
- ONT
Nonstop4h 33m
United Airlines
Deal found 3/17![United Airlines logo]()
$387
This Alaska Airlines deal was found by Cheapflights users on 3/17. Clicking the “Pick Dates” 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.
ter 6/27:00 am
ONT
- STL
1 stop7h 37m
Alaska Airlines
ter 6/166:00 am
STL
- ONT
1 stop9h 13m
Alaska Airlines
Deal found 3/17![Alaska Airlines logo]()
$434
This Kiwi.com deal was found by Cheapflights users on 3/17. Clicking the “Pick Dates” 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.
qua 6/103:34 pm
ONT
- RFD
1 stop18h 49m
Multiple Airlines
dom 6/141:13 pm
RFD
- ONT
1 stop8h 35m
Multiple Airlines
Deal found 3/17![Multiple Airlines logo]()
$469
This Delta deal was found by Cheapflights users on 3/17. Clicking the “Pick Dates” 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.
sáb 4/187:05 am
ONT
- MDW
1 stop7h 21m
Delta
sáb 4/256:00 am
MDW
- ONT
1 stop7h 36m
Delta
Deal found 3/17![Delta logo]()
$337
This Southwest deal was found by Cheapflights users on 3/15. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
qui 5/1412:40 pm
ONT
- MDW
1 stop7h 40m
Southwest
qua 5/2011:00 am
MDW
- ONT
Nonstop4h 15m
Southwest
Deal found 3/15![Southwest logo]()
$382
This Delta deal was found by Cheapflights users on 3/14. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
sáb 4/187:05 am
ONT
- ORD
1 stop9h 43m
Delta
sáb 4/255:15 am
ORD
- ONT
1 stop8h 21m
Delta
Deal found 3/14![Delta logo]()
$355
This United Airlines deal was found by Cheapflights users on 3/13. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
qui 6/256:30 am
ONT
- MLI
1 stop9h 22m
United Airlines
seg 6/293:52 pm
MLI
- ONT
1 stop8h 59m
United Airlines
Deal found 3/13![United Airlines logo]()
$422
This Delta deal was found by Cheapflights users on 3/16. Clicking the “Pick Dates” 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.
ter 5/265:50 pm
ONT
- MDW
2 stops12h 52m
Delta
qua 6/31:22 pm
MDW
- ONT
2 stops12h 12m
Delta
Deal found 3/16![Delta logo]()
$368
This Alaska Airlines deal was found by Cheapflights users on 3/15. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Alaska Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
ter 4/216:00 am
ONT
- STL
1 stop15h 59m
Alaska Airlines
sex 4/244:46 pm
STL
- ONT
1 stop9h 13m
Alaska Airlines
Deal found 3/15![Alaska Airlines logo]()
$448
This Southwest deal was found by Cheapflights users on 3/13. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
sex 4/1011:55 pm
ONT
- STL
1 stop8h 35m
Southwest
dom 4/128:30 am
STL
- ONT
1 stop5h 20m
Southwest
Deal found 3/13![Southwest logo]()
$422
This United Airlines deal was found by Cheapflights users on 3/16. Clicking the “Pick Dates” 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.
ter 4/141:34 pm
ONT
- ORD
1 stop5h 46m
United Airlines
sáb 4/187:00 am
ORD
- ONT
2 stops12h 47m
United Airlines
Deal found 3/16![United Airlines logo]()
$422
This American Airlines deal was found by Cheapflights users on 3/15. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure American Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
qua 8/512:35 pm
ONT
- PIA
1 stop8h 45m
American Airlines
dom 8/94:43 pm
PIA
- ONT
1 stop6h 25m
American Airlines
Deal found 3/15![American Airlines logo]()
$474
This Delta deal was found by Cheapflights users on 3/14. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
qua 5/206:00 am
ONT
- MDW
2 stops10h 33m
Delta
qua 5/271:59 pm
MDW
- ONT
2 stops11h 35m
Delta
Deal found 3/14![Delta logo]()
$368
This Southwest deal was found by Cheapflights users on 3/13. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
sex 5/111:55 pm
ONT
- MDW
Nonstop3h 45m
Southwest
dom 5/310:35 am
MDW
- ONT
1 stop9h 10m
Southwest
Deal found 3/13![Southwest logo]()
$434
This Kiwi.com deal was found by Cheapflights users on 3/13. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
sáb 7/49:11 pm
ONT
- RFD
1 stop13h 13m
Multiple Airlines
qui 7/91:14 pm
RFD
- ONT
1 stop21h 53m
Multiple Airlines
Deal found 3/13![Multiple Airlines logo]()
$538
This United Airlines deal was found by Cheapflights users on 3/16. Clicking the “Pick Dates” 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.
ter 5/261:50 pm
ONT
- ORD
1 stop9h 09m
United Airlines
qua 6/38:13 pm
ORD
- ONT
Nonstop4h 33m
United Airlines
Deal found 3/16![United Airlines logo]()
$447
This Southwest deal was found by Cheapflights users on 3/17. Clicking the “Pick Dates” 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.
qui 4/3011:55 pm
ONT
- MDW
Nonstop3h 45m
Southwest
dom 5/37:45 am
MDW
- ONT
2 stops9h 25m
Southwest
Deal found 3/17![Southwest logo]()
$439
This United Airlines deal was found by Cheapflights users on 3/15. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
qua 4/81:27 pm
ONT
- ORD
1 stop8h 02m
United Airlines
qua 4/158:05 pm
ORD
- ONT
Nonstop4h 26m
United Airlines
Deal found 3/15![United Airlines logo]()
$447
This Delta deal was found by Cheapflights users on 3/14. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
sex 4/310:25 pm
ONT
- STL
1 stop8h 37m
Delta
dom 4/56:12 pm
STL
- ONT
1 stop7h 39m
Delta
Deal found 3/14![Delta logo]()
$416
This American Airlines deal was found by Cheapflights users on 3/12. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure American Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
ter 3/3110:36 pm
ONT
- EVV
1 stop10h 04m
American Airlines
ter 4/74:03 pm
EVV
- ONT
1 stop8h 33m
American Airlines
Deal found 3/12![American Airlines logo]()
$564
This United Airlines deal was found by Cheapflights users on 3/14. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
sáb 4/181:34 pm
ONT
- ORD
1 stop7h 24m
United Airlines
qua 4/228:05 pm
ORD
- ONT
Nonstop4h 26m
United Airlines
Deal found 3/14![United Airlines logo]()
$447
This Southwest deal was found by Cheapflights users on 3/13. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
sex 5/228:45 pm
ONT
- MDW
1 stop7h 00m
Southwest
qua 5/274:00 pm
MDW
- ONT
2 stops8h 10m
Southwest
Deal found 3/13![Southwest logo]()
$449
This Delta deal was found by Cheapflights users on 3/17. Clicking the “Pick Dates” 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.
sex 5/84:57 pm
ONT
- STL
1 stop5h 33m
Delta
ter 5/127:00 am
STL
- ONT
1 stop7h 19m
Delta
Deal found 3/17![Delta logo]()
$417
This American Airlines deal was found by Cheapflights users on 3/16. Clicking the “Pick Dates” 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.
ter 3/3110:36 pm
ONT
- EVV
1 stop10h 04m
American Airlines
sáb 4/46:30 am
EVV
- ONT
1 stop9h 18m
American Airlines
Deal found 3/16![American Airlines logo]()
$581
This United Airlines deal was found by Cheapflights users on 3/17. Clicking the “Pick Dates” 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.
qui 4/167:00 am
ONT
- ORD
Nonstop4h 03m
United Airlines
sex 4/178:05 pm
ORD
- ONT
Nonstop4h 26m
United Airlines
Deal found 3/17![United Airlines logo]()
$447
This Delta deal was found by Cheapflights users on 3/17. Clicking the “Pick Dates” 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.
seg 4/205:05 pm
ONT
- STL
1 stop5h 20m
Delta
sáb 4/256:00 am
STL
- ONT
1 stop7h 36m
Delta
Deal found 3/17![Delta logo]()
$423
This Kiwi.com deal was found by Cheapflights users on 3/14. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
sáb 4/412:38 pm
ONT
- RFD
2 stops19h 09m
Multiple Airlines
dom 4/512:45 pm
RFD
- ONT
1 stop7h 03m
Multiple Airlines
Deal found 3/14![Multiple Airlines logo]()
$690
Last-minute flights from Ontario to IllinoisDiscover last-minute flight deals from Ontario to Illinois. Data last updated março 18, 2026 and is based on user searches.
Discover last-minute flight deals from Ontario to Illinois. Data last updated março 18, 2026 and is based on user searches.
This Frontier deal was found by Cheapflights users on 3/16. Clicking the “Pick Dates” 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.
qui 4/210:50 am
ONT
- STL
1 stop8h 27m
Frontier
qua 4/88:16 pm
STL
- ONT
1 stop5h 40m
Frontier
Deal found 3/16![Frontier logo]()
$240
This Gotogate deal was found by Cheapflights users on 3/15. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Gotogate is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
ter 4/76:20 am
ONT
- STL
1 stop25h 28m
Frontier
qua 4/88:16 pm
STL
- ONT
1 stop5h 40m
Frontier
Deal found 3/15![Frontier logo]()
$216
This CheapOair deal was found by Cheapflights users on 3/16. Clicking the “Pick Dates” 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.
ter 4/76:20 am
ONT
- STL
1 stop25h 28m
Frontier
sex 4/179:55 pm
STL
- ONT
1 stop14h 49m
Frontier
Deal found 3/16![Frontier logo]()
$221
This Frontier deal was found by Cheapflights users on 3/16. Clicking the “Pick Dates” 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.
qui 4/910:27 pm
ONT
- STL
1 stop11h 00m
Frontier
seg 4/1312:22 pm
STL
- ONT
1 stop9h 45m
Frontier
Deal found 3/16![Frontier logo]()
$230
This Kiwi.com deal was found by Cheapflights users on 3/13. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
sex 4/106:20 am
ONT
- STL
1 stop25h 28m
Frontier
seg 4/138:19 pm
STL
- ONT
1 stop29h 36m
Frontier
Deal found 3/13![Frontier logo]()
$224
This CheapOair deal was found by Cheapflights users on 3/16. Clicking the “Pick Dates” 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.
sex 4/106:20 am
ONT
- STL
1 stop25h 28m
Frontier
seg 5/119:18 pm
STL
- ONT
1 stop24h 14m
Frontier
Deal found 3/16![Frontier logo]()
$241
This Mytrip deal was found by Cheapflights users on 3/14. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Mytrip is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
qua 4/157:44 pm
ONT
- STL
1 stop23h 16m
Frontier
sex 4/179:55 pm
STL
- ONT
1 stop22h 54m
Frontier
Deal found 3/14![Frontier logo]()
$219
This Frontier deal was found by Cheapflights users on 3/13. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
qui 4/1611:47 am
ONT
- STL
1 stop7h 13m
Frontier
qui 4/239:55 pm
STL
- ONT
1 stop12h 29m
Frontier
Deal found 3/13![Frontier logo]()
$210
This Booking.com deal was found by Cheapflights users on 3/13. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Booking.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
qui 4/1611:47 am
ONT
- STL
1 stop7h 13m
Frontier
dom 4/199:55 pm
STL
- ONT
1 stop14h 19m
Frontier
Deal found 3/13![Frontier logo]()
$217
This Booking.com deal was found by Cheapflights users on 3/16. Clicking the “Pick Dates” 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.
sex 4/1712:59 am
ONT
- STL
1 stop16h 33m
Frontier
sex 4/249:58 pm
STL
- ONT
1 stop22h 51m
Frontier
Deal found 3/16![Frontier logo]()
$212
This Frontier deal was found by Cheapflights users on 3/17. Clicking the “Pick Dates” 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.
sex 4/1712:59 am
ONT
- STL
1 stop16h 33m
Frontier
sáb 4/258:17 pm
STL
- ONT
1 stop13h 09m
Frontier
Deal found 3/17![Frontier logo]()
$213
This Kiwi.com deal was found by Cheapflights users on 3/17. Clicking the “Pick Dates” 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.
sex 4/175:33 pm
ONT
- STL
1 stop23h 59m
Frontier
sex 4/249:58 pm
STL
- ONT
2 stops27h 57m
Frontier
Deal found 3/17![Frontier logo]()
$249
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 março 18, 2026.
Search for one-way flight options from Ontario to Illinois. Find affordable one-way fares based on user searches. Data last updated março 18, 2026.
This Kiwi.com deal was found by Cheapflights users on 3/13. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
qua 5/1310:50 am
ONT
- ORD
1 stop7h 47m
Frontier
Deal found 3/13![Frontier logo]()
$93
This Trip.com deal was found by Cheapflights users on 3/17. Clicking the “Pick Dates” 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.
sex 4/106:20 am
ONT
- STL
1 stop25h 28m
Frontier
Deal found 3/17![Frontier logo]()
$99
This Kiwi.com deal was found by Cheapflights users on 3/17. Clicking the “Pick Dates” 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.
qua 5/610:50 am
ONT
- ORD
1 stop7h 47m
Frontier
Deal found 3/17![Frontier logo]()
$102
This Trip.com deal was found by Cheapflights users on 3/15. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Trip.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
ter 4/2111:44 am
ONT
- ORD
1 stop16h 24m
Frontier
Deal found 3/15![Frontier logo]()
$103
This WAYA deal was found by Cheapflights users on 3/17. Clicking the “Pick Dates” 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.
ter 4/147:44 pm
ONT
- ORD
1 stop8h 24m
Frontier
Deal found 3/17![Frontier logo]()
$104
This Frontier deal was found by Cheapflights users on 3/13. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
qui 4/2311:47 am
ONT
- STL
1 stop7h 13m
Frontier
Deal found 3/13![Frontier logo]()
$105
This CheapOair deal was found by Cheapflights users on 3/17. Clicking the “Pick Dates” 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.
qua 4/227:44 pm
ONT
- ORD
1 stop8h 24m
Frontier
Deal found 3/17![Frontier logo]()
$105
This Frontier deal was found by Cheapflights users on 3/17. Clicking the “Pick Dates” 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.
dom 4/1912:59 am
ONT
- ORD
1 stop6h 51m
Frontier
Deal found 3/17![Frontier logo]()
$106
This Trip.com deal was found by Cheapflights users on 3/15. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Trip.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
qua 4/1512:59 am
ONT
- ORD
1 stop6h 51m
Frontier
Deal found 3/15![Frontier logo]()
$107
This Super.com deal was found by Cheapflights users on 3/13. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
seg 4/278:26 am
ONT
- ORD
1 stop28h 51m
Frontier
Deal found 3/13![Frontier logo]()
$109
This Super.com deal was found by Cheapflights users on 3/16. Clicking the “Pick Dates” 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.
sex 5/158:06 pm
ONT
- ORD
1 stop24h 55m
Frontier
Deal found 3/16![Frontier logo]()
$110
This Booking.com deal was found by Cheapflights users on 3/15. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Booking.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
qua 4/110:03 pm
ONT
- STL
1 stop21h 14m
Frontier
Deal found 3/15![Frontier logo]()
$111
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 março 18, 2026.
Most accurate provider | FlightHub 3 stars |
|---|---|
Most trusted provider | FlightHub 3 stars |
Round-trip from | $210 (Frontier) |
One-way from | $93 (Kiwi.com) |
Popular in | February |
Cheapest in | September |
Average price | $351 |
Good round-trip deal | $341 or less |
Good one-way deal | $218 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 março 18, 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
Quickest round-trip
OntarioChicago
ONT - MDW
ONTMDW
Ontario
qui 4/16
11:55 pm-5:40 am
Nonstop3h 45m
Chicago Midway
seg 4/20
11:00 am-1:15 pm
Nonstop4h 15m
$317
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
ter 4/7
6:00 am-1:17 pm
1 stop5h 17m
Lambert-St Louis
ter 4/7
6:12 pm-11:51 pm
1 stop7h 39m
$333
OntarioChicago
ONT - MDW
ONTMDW
Ontario
sáb 4/18
7:05 am-4:26 pm
1 stop7h 21m
Chicago Midway
sáb 4/25
6:00 am-11:36 am
1 stop7h 36m
$337
OntarioMoline
ONT - MLI
ONTMLI
Ontario
qua 4/15
12:19 pm-11:54 pm
2 stops9h 35m
Moline Quad-City
qua 4/22
12:52 pm-9:07 pm
1 stop10h 15m
$354
OntarioChicago
ONT - ORD
ONTORD
Ontario
sáb 4/18
7:05 am-6:48 pm
1 stop9h 43m
Chicago O'Hare Intl
sáb 4/25
5:15 am-11:36 am
1 stop8h 21m
$355
OntarioChicago
ONT - MDW
ONTMDW
Ontario
ter 5/26
5:50 pm-8:42 am
2 stops12h 52m
Chicago Midway
qua 6/3
1:22 pm-11:34 pm
2 stops12h 12m
$368
OntarioChicago
ONT - MDW
ONTMDW
Ontario
qua 5/20
6:00 am-6:33 pm
2 stops10h 33m
Chicago Midway
qua 5/27
1:59 pm-11:34 pm
2 stops11h 35m
$368
OntarioChicago
ONT - MDW
ONTMDW
Ontario
qui 5/14
12:40 pm-10:20 pm
1 stop7h 40m
Chicago Midway
qua 5/20
11:00 am-1:15 pm
Nonstop4h 15m
$382
OntarioChicago
ONT - ORD
ONTORD
Ontario
qua 6/3
6:30 am-12:45 pm
Nonstop4h 15m
Chicago O'Hare Intl
qua 6/10
8:13 pm-10:46 pm
Nonstop4h 33m
$387
OntarioSt. Louis
ONT - STL
ONTSTL
Ontario
sex 4/3
10:25 pm-9:02 am
1 stop8h 37m
Lambert-St Louis
dom 4/5
6:12 pm-11:51 pm
1 stop7h 39m
$416
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-RFD
ONT-MDW
ONT-ORD
ONT-BMI
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-RFD
ONT-MDW
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 março 18, 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 março 18, 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.
Entertainment
7.5
Comfort
8.0
Overall
8.0
Crew
8.6
Food
7.0
Boarding
8.1
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Entertainment
7.5
Comfort
8.0
Overall
8.0
Crew
8.6
Food
7.0
Boarding
8.1
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Entertainment
7.5
Comfort
8.0
Overall
8.0
Crew
8.6
Food
7.0
Boarding
8.1
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Entertainment
7.5
Comfort
8.0
Overall
8.0
Crew
8.6
Food
7.0
Boarding
8.1
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Entertainment
7.5
Comfort
8.0
Overall
8.0
Crew
8.6
Food
7.0
Boarding
8.1
Reviews
1 / 20
10.0
ExcellentWilliam Drew,Nov 2025
SJC - HNL
Entertainment
7.5
Comfort
8.0
Overall
8.0
Crew
8.6
Food
7.0
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.
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 março 18, 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 março 18, 2026.
| Airline | Cheapest | Average | Flexibility | On-time |
|---|---|---|---|---|
| Cheapest$98 | Average$237 | FlexibilityNo cancel fee | On-time62% | |
| Cheapest$226 | Average$458 | FlexibilityNo cancel fee | On-time69% | |
| Cheapest$237 | Average$388 | FlexibilityNo cancel fee | On-time63% | |
| Cheapest$246 | Average$482 | FlexibilityNo cancel fee | On-time71% | |
| Cheapest$256 | Average$373 | FlexibilityNo cancel fee | On-timeN/A |