$43+ Cheap flights from Colorado 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 7/15. Fares are subject to change and may not be available on all flights or dates of travel.
DEN — ORD
Jun 12 — Jun 191
Round-trip
1 adult, Economy
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Cheapest flights from Colorado to IllinoisExplore the most affordable flight options available from Colorado to Illinois. Find the lowest fares from popular airlines and budget airlines, with prices last updated on May 13, 2026.
Explore the most affordable flight options available from Colorado to Illinois. Find the lowest fares from popular airlines and budget airlines, with prices last updated on May 13, 2026.
This Cheapflightsfares deal was found by Cheapflights users on 5/8. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 8/202:17 pm
DEN
- PIA
Nonstop2h 07m
Allegiant Air
Sun 8/2310:07 am
PIA
- DEN
Nonstop2h 19m
Allegiant Air
Deal found 5/8![Allegiant Air logo]()
$117
This Kiwi.com deal was found by Cheapflights users on 5/13. 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.
Tue 8/114:10 pm
DEN
- STL
Nonstop2h 13m
Frontier
Tue 8/186:33 pm
STL
- DEN
1 stop15h 25m
Frontier
Deal found 5/13![Frontier logo]()
$133
This Frontier deal was found by Cheapflights users on 5/12. 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 Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 10/144:12 pm
DEN
- STL
Nonstop2h 03m
Frontier
Mon 10/198:10 pm
STL
- DEN
Nonstop2h 39m
Frontier
Deal found 5/12![Frontier logo]()
$134
This Trip.com deal was found by Cheapflights users on 5/10. Clicking the “Pick Dates” 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 6/24:15 pm
DEN
- STL
Nonstop2h 08m
Frontier
Tue 6/96:03 pm
STL
- DEN
1 stop7h 35m
Frontier
Deal found 5/10![Frontier logo]()
$137
This Kiwi.com deal was found by Cheapflights users on 5/12. 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 Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 8/114:10 pm
DEN
- STL
Nonstop2h 13m
Frontier
Mon 8/174:52 pm
STL
- DEN
1 stop17h 06m
Frontier
Deal found 5/12![Frontier logo]()
$138
This Frontier deal was found by Cheapflights users on 5/12. 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 Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 8/44:10 pm
DEN
- STL
Nonstop2h 13m
Frontier
Wed 8/123:34 pm
STL
- DEN
1 stop5h 58m
Frontier
Deal found 5/12![Frontier logo]()
$139
This Cheapflightsfares deal was found by Cheapflights users on 5/10. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 6/34:15 pm
DEN
- STL
Nonstop2h 08m
Frontier
Mon 6/88:08 pm
STL
- DEN
Nonstop2h 33m
Frontier
Deal found 5/10![Frontier logo]()
$143
This Frontier deal was found by Cheapflights users on 5/12. 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 Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 7/154:10 pm
DEN
- STL
Nonstop2h 13m
Frontier
Sat 7/188:08 pm
STL
- DEN
Nonstop2h 36m
Frontier
Deal found 5/12![Frontier logo]()
$148
This CheapOair deal was found by Cheapflights users on 5/12. 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 CheapOair is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 7/87:26 pm
DEN
- STL
1 stop17h 41m
Frontier
Tue 7/148:08 pm
STL
- DEN
Nonstop2h 36m
Frontier
Deal found 5/12![Frontier logo]()
$149
This Kiwi.com deal was found by Cheapflights users on 5/13. 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.
Wed 6/1710:09 am
DEN
- STL
1 stop7h 09m
Frontier
Wed 6/248:08 pm
STL
- DEN
Nonstop2h 36m
Frontier
Deal found 5/13![Frontier logo]()
$151
This Cheapflightsfares deal was found by Cheapflights users on 5/12. 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 Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 5/276:30 am
DEN
- ORD
1 stop12h 11m
Frontier
Fri 5/299:37 pm
ORD
- DEN
Nonstop3h 07m
Frontier
Deal found 5/12![Frontier logo]()
$180
This Frontier deal was found by Cheapflights users on 5/12. 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 Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 5/294:54 pm
DEN
- ORD
Nonstop2h 38m
Frontier
Fri 6/51:29 pm
ORD
- DEN
1 stop9h 55m
Frontier
Deal found 5/12![Frontier logo]()
$181
Best flights from Colorado to IllinoisDiscover carefully curated flight deals from Colorado to Illinois that have cost, travel time, and layovers in mind to ensure you get the best travel experience. Data last updated May 13, 2026.
Discover carefully curated flight deals from Colorado to Illinois that have cost, travel time, and layovers in mind to ensure you get the best travel experience. Data last updated May 13, 2026.
This United Airlines deal was found by Cheapflights users on 5/12. 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 United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 7/86:00 pm
DEN
- ORD
Nonstop2h 39m
United Airlines
Tue 7/145:00 am
ORD
- DEN
Nonstop2h 41m
United Airlines
Deal found 5/12![United Airlines logo]()
$217
This Delta deal was found by Cheapflights users on 5/8. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 6/46:05 am
DEN
- ORD
1 stop5h 56m
Delta
Mon 6/83:22 pm
ORD
- DEN
1 stop7h 35m
Delta
Deal found 5/8![Delta logo]()
$241
This Southwest deal was found by Cheapflights users on 5/12. 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 Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 7/275:55 am
DEN
- MDW
Nonstop2h 25m
Southwest
Tue 7/285:30 am
MDW
- DEN
Nonstop2h 35m
Southwest
Deal found 5/12![Southwest logo]()
$241
This American Airlines deal was found by Cheapflights users on 5/12. 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.
Fri 6/195:15 pm
COS
- STL
1 stop5h 44m
American Airlines
Sun 6/215:29 am
STL
- COS
1 stop5h 24m
American Airlines
Deal found 5/12![American Airlines logo]()
$333
This Kiwi.com deal was found by Cheapflights users on 5/11. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 7/156:30 am
DEN
- RFD
2 stops27h 07m
Multiple Airlines
Sun 7/199:19 am
RFD
- DEN
1 stop5h 56m
Multiple Airlines
Deal found 5/11![Multiple Airlines logo]()
$344
This United Airlines deal was found by Cheapflights users on 5/11. Clicking the “Pick Dates” 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.
Sun 6/149:05 pm
DEN
- ORD
Nonstop2h 39m
United Airlines
Tue 6/166:00 am
ORD
- DEN
Nonstop2h 42m
United Airlines
Deal found 5/11![United Airlines logo]()
$241
This Southwest deal was found by Cheapflights users on 5/8. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 7/76:15 am
DEN
- MDW
Nonstop2h 25m
Southwest
Thu 7/95:15 am
MDW
- DEN
Nonstop2h 35m
Southwest
Deal found 5/8![Southwest logo]()
$241
This Delta deal was found by Cheapflights users on 5/11. Clicking the “Pick Dates” 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 6/46:05 am
DEN
- MDW
1 stop5h 37m
Delta
Tue 6/96:00 am
MDW
- DEN
1 stop7h 59m
Delta
Deal found 5/11![Delta logo]()
$247
This Southwest deal was found by Cheapflights users on 5/12. 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 Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 8/284:55 pm
DEN
- MDW
Nonstop2h 20m
Southwest
Tue 9/18:20 am
MDW
- DEN
1 stop5h 00m
Southwest
Deal found 5/12![Southwest logo]()
$247
This Delta deal was found by Cheapflights users on 5/10. Clicking the “Pick Dates” 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.
Fri 7/36:00 am
DEN
- ORD
1 stop4h 31m
Delta
Tue 7/73:22 pm
ORD
- DEN
1 stop6h 31m
Delta
Deal found 5/10![Delta logo]()
$261
This United Airlines deal was found by Cheapflights users on 5/13. 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.
Sat 7/187:10 pm
DEN
- ORD
Nonstop2h 39m
United Airlines
Sun 7/195:00 am
ORD
- DEN
Nonstop2h 41m
United Airlines
Deal found 5/13![United Airlines logo]()
$265
This Alaska Airlines deal was found by Cheapflights users on 5/11. Clicking the “Pick Dates” 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.
Fri 9/47:06 pm
DEN
- STL
2 stops17h 58m
Alaska Airlines
Mon 9/75:59 pm
STL
- DEN
1 stop28h 47m
Alaska Airlines
Deal found 5/11![Alaska Airlines logo]()
$595
This Southwest deal was found by Cheapflights users on 5/12. 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 Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 6/236:15 am
DEN
- MDW
Nonstop2h 25m
Southwest
Sat 6/2712:50 pm
MDW
- DEN
1 stop4h 45m
Southwest
Deal found 5/12![Southwest logo]()
$247
This United Airlines deal was found by Cheapflights users on 5/12. 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 United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 6/126:15 pm
DEN
- ORD
Nonstop2h 39m
United Airlines
Sun 6/145:00 am
ORD
- DEN
Nonstop2h 42m
United Airlines
Deal found 5/12![United Airlines logo]()
$265
This Delta deal was found by Cheapflights users on 5/11. Clicking the “Pick Dates” 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.
Fri 6/123:15 pm
DEN
- MDW
1 stop6h 02m
Delta
Mon 6/155:11 pm
MDW
- DEN
1 stop8h 11m
Delta
Deal found 5/11![Delta logo]()
$271
This Southwest deal was found by Cheapflights users on 5/9. Clicking the “Pick Dates” 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 6/197:05 pm
DEN
- MDW
1 stop4h 55m
Southwest
Tue 6/239:05 pm
MDW
- DEN
Nonstop2h 45m
Southwest
Deal found 5/9![Southwest logo]()
$261
This United Airlines deal was found by Cheapflights users on 5/12. 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 United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 6/274:59 pm
DEN
- ORD
Nonstop2h 41m
United Airlines
Sun 7/55:00 am
ORD
- DEN
Nonstop2h 41m
United Airlines
Deal found 5/12![United Airlines logo]()
$265
This Delta deal was found by Cheapflights users on 5/10. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 8/136:00 am
DEN
- MDW
1 stop6h 08m
Delta
Sun 8/167:25 pm
MDW
- DEN
1 stop5h 09m
Delta
Deal found 5/10![Delta logo]()
$271
This Kiwi.com deal was found by Cheapflights users on 5/9. Clicking the “Pick Dates” 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 6/1210:36 pm
DEN
- RFD
1 stop12h 38m
Multiple Airlines
Sun 6/149:19 am
RFD
- DEN
1 stop6h 01m
Multiple Airlines
Deal found 5/9![Multiple Airlines logo]()
$378
This Southwest deal was found by Cheapflights users on 5/11. Clicking the “Pick Dates” 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 6/227:05 pm
DEN
- MDW
1 stop4h 55m
Southwest
Tue 6/306:00 pm
MDW
- DEN
Nonstop2h 45m
Southwest
Deal found 5/11![Southwest logo]()
$261
This United Airlines deal was found by Cheapflights users on 5/8. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 6/126:00 am
DEN
- ORD
Nonstop2h 38m
United Airlines
Fri 6/129:54 pm
ORD
- DEN
Nonstop2h 58m
United Airlines
Deal found 5/8![United Airlines logo]()
$275
This Delta deal was found by Cheapflights users on 5/8. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 5/2912:55 am
DEN
- MDW
1 stop6h 48m
Delta
Mon 6/11:59 pm
MDW
- DEN
1 stop7h 16m
Delta
Deal found 5/8![Delta logo]()
$280
This Kiwi.com deal was found by Cheapflights users on 5/8. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 6/1611:46 pm
DEN
- RFD
2 stops33h 51m
Multiple Airlines
Thu 6/259:19 am
RFD
- DEN
1 stop6h 01m
Multiple Airlines
Deal found 5/8![Multiple Airlines logo]()
$385
This Southwest deal was found by Cheapflights users on 5/10. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 8/204:55 pm
DEN
- MDW
Nonstop2h 20m
Southwest
Sun 8/237:30 am
MDW
- DEN
1 stop4h 25m
Southwest
Deal found 5/10![Southwest logo]()
$271
This Delta deal was found by Cheapflights users on 5/9. Clicking the “Pick Dates” 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 7/23:15 pm
DEN
- ORD
1 stop7h 44m
Delta
Thu 7/93:22 pm
ORD
- DEN
1 stop6h 31m
Delta
Deal found 5/9![Delta logo]()
$285
This United Airlines deal was found by Cheapflights users on 5/9. Clicking the “Pick Dates” 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 6/85:33 pm
DEN
- PIA
Nonstop2h 28m
United Airlines
Mon 6/154:45 pm
PIA
- DEN
1 stop8h 07m
United Airlines
Deal found 5/9![United Airlines logo]()
$299
This Southwest deal was found by Cheapflights users on 5/8. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 5/276:15 am
DEN
- ORD
1 stop5h 35m
Southwest
Tue 6/27:45 am
ORD
- DEN
2 stops8h 20m
Southwest
Deal found 5/8![Southwest logo]()
$274
This Delta deal was found by Cheapflights users on 5/10. Clicking the “Pick Dates” 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 5/3112:56 am
DEN
- MLI
1 stop8h 24m
Delta
Sat 6/65:17 pm
MLI
- DEN
1 stop8h 16m
Delta
Deal found 5/10![Delta logo]()
$289
This United Airlines deal was found by Cheapflights users on 5/10. Clicking the “Pick Dates” 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 5/295:33 pm
DEN
- PIA
Nonstop2h 28m
United Airlines
Mon 6/11:13 pm
PIA
- DEN
1 stop8h 09m
United Airlines
Deal found 5/10![United Airlines logo]()
$299
This Southwest deal was found by Cheapflights users on 5/11. Clicking the “Pick Dates” 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 6/127:05 pm
DEN
- MDW
1 stop4h 55m
Southwest
Mon 6/155:15 am
MDW
- DEN
Nonstop2h 35m
Southwest
Deal found 5/11![Southwest logo]()
$275
Last-minute flights from Colorado to IllinoisDiscover last-minute flight deals from Colorado to Illinois. Data last updated May 13, 2026 and is based on user searches.
Discover last-minute flight deals from Colorado to Illinois. Data last updated May 13, 2026 and is based on user searches.
This Cheapflightsfares deal was found by Cheapflights users on 5/11. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 5/194:54 pm
DEN
- ORD
Nonstop2h 38m
Frontier
Tue 6/29:37 pm
ORD
- DEN
Nonstop3h 07m
Frontier
Deal found 5/11![Frontier logo]()
$182
This deal was found by Cheapflights users on 5/10. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 5/234:54 pm
DEN
- ORD
Nonstop2h 38m
Frontier
Sat 5/309:37 pm
ORD
- DEN
Nonstop3h 07m
Frontier
Deal found 5/10![Frontier logo]()
$184
This Cheapflightsfares deal was found by Cheapflights users on 5/8. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 5/234:54 pm
DEN
- ORD
Nonstop2h 38m
Frontier
Sun 5/249:37 pm
ORD
- DEN
Nonstop3h 07m
Frontier
Deal found 5/8![Frontier logo]()
$189
This Cheapflightsfares deal was found by Cheapflights users on 5/10. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 5/309:52 am
DEN
- STL
1 stop8h 39m
Frontier
Tue 6/28:08 pm
STL
- DEN
Nonstop2h 33m
Frontier
Deal found 5/10![Frontier logo]()
$152
This Trip.com deal was found by Cheapflights users on 5/10. Clicking the “Pick Dates” 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 6/24:15 pm
DEN
- STL
Nonstop2h 08m
Frontier
Tue 6/96:03 pm
STL
- DEN
1 stop7h 35m
Frontier
Deal found 5/10![Frontier logo]()
$137
This deal was found by Cheapflights users on 5/12. 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 is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 6/24:15 pm
DEN
- STL
Nonstop2h 08m
Frontier
Wed 6/108:08 pm
STL
- DEN
Nonstop2h 36m
Frontier
Deal found 5/12![Frontier logo]()
$148
This Cheapflightsfares deal was found by Cheapflights users on 5/10. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 6/34:15 pm
DEN
- STL
Nonstop2h 08m
Frontier
Mon 6/88:08 pm
STL
- DEN
Nonstop2h 33m
Frontier
Deal found 5/10![Frontier logo]()
$143
This Kiwi.com deal was found by Cheapflights users on 5/11. Clicking the “Pick Dates” 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 6/34:15 pm
DEN
- STL
Nonstop2h 08m
Frontier
Sun 6/76:33 pm
STL
- DEN
1 stop28h 51m
Frontier
Deal found 5/11![Frontier logo]()
$153
This Cheapflightsfares deal was found by Cheapflights users on 5/10. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 6/34:15 pm
DEN
- STL
Nonstop2h 08m
Frontier
Fri 6/54:19 pm
STL
- DEN
1 stop7h 52m
Frontier
Deal found 5/10![Frontier logo]()
$158
This Frontier deal was found by Cheapflights users on 5/11. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 6/94:12 pm
DEN
- STL
Nonstop2h 11m
Frontier
Wed 6/107:03 pm
STL
- DEN
1 stop6h 35m
Frontier
Deal found 5/11![Frontier logo]()
$139
This Expedia deal was found by Cheapflights users on 5/13. 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 Expedia is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 6/109:58 am
DEN
- MDW
1 stop11h 13m
Frontier
Wed 6/1712:04 pm
MDW
- DEN
1 stop11h 12m
Frontier
Deal found 5/13![Frontier logo]()
$190
This Kiwi.com deal was found by Cheapflights users on 5/13. 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.
Wed 6/1710:09 am
DEN
- STL
1 stop7h 09m
Frontier
Wed 6/248:08 pm
STL
- DEN
Nonstop2h 36m
Frontier
Deal found 5/13![Frontier logo]()
$151
One-way flights from Colorado to IllinoisSearch for one-way flight options from Colorado to Illinois. Find affordable one-way fares based on user searches. Data last updated May 13, 2026.
Search for one-way flight options from Colorado to Illinois. Find affordable one-way fares based on user searches. Data last updated May 13, 2026.
This Kiwi.com deal was found by Cheapflights users on 5/10. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 7/154:10 pm
DEN
- STL
Nonstop2h 13m
Frontier
Deal found 5/10![Frontier logo]()
$43
This Frontier deal was found by Cheapflights users on 5/12. 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 Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 6/94:12 pm
DEN
- STL
Nonstop2h 11m
Frontier
Deal found 5/12![Frontier logo]()
$44
This Frontier deal was found by Cheapflights users on 5/12. 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 Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 6/64:15 pm
DEN
- STL
Nonstop2h 08m
Frontier
Deal found 5/12![Frontier logo]()
$79
This Kiwi.com deal was found by Cheapflights users on 5/9. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 9/84:12 pm
DEN
- STL
Nonstop2h 11m
Frontier
Deal found 5/9![Frontier logo]()
$86
This Kiwi.com deal was found by Cheapflights users on 5/9. Clicking the “Pick Dates” 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 7/65:05 pm
DEN
- ORD
Nonstop2h 47m
Frontier
Deal found 5/9![Frontier logo]()
$87
This Cheapflightsfares deal was found by Cheapflights users on 5/12. 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 Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 5/164:54 pm
DEN
- ORD
Nonstop2h 38m
Frontier
Deal found 5/12![Frontier logo]()
$89
This Super.com deal was found by Cheapflights users on 5/9. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 6/44:15 pm
DEN
- STL
Nonstop2h 08m
Frontier
Deal found 5/9![Frontier logo]()
$89
This Frontier deal was found by Cheapflights users on 5/9. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 6/24:15 pm
DEN
- STL
Nonstop2h 08m
Frontier
Deal found 5/9![Frontier logo]()
$90
This Super.com deal was found by Cheapflights users on 5/11. Clicking the “Pick Dates” 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 6/1011:46 pm
DEN
- ORD
1 stop7h 17m
Frontier
Deal found 5/11![Frontier logo]()
$91
This Frontier deal was found by Cheapflights users on 5/12. 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 Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 10/194:12 pm
DEN
- STL
Nonstop2h 03m
Frontier
Deal found 5/12![Frontier logo]()
$91
This Super.com deal was found by Cheapflights users on 5/12. 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 Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 8/117:26 pm
DEN
- ORD
1 stop9h 02m
Frontier
Deal found 5/12![Frontier logo]()
$92
This Super.com deal was found by Cheapflights users on 5/8. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 7/2211:46 pm
DEN
- ORD
1 stop7h 07m
Frontier
Deal found 5/8![Frontier logo]()
$93
Find flight deals from Colorado to Illinois
Keep the following information in mind while searching for Colorado to Illinois flight deals. Data was last updated May 13, 2026.
Most accurate provider | FlightHub 3 stars |
|---|---|
Most trusted provider | FlightHub 3 stars |
Round-trip from | $133 (Super.com) |
One-way from | $43 (Kiwi.com) |
Popular in | March |
Cheapest in | August |
Average price | $266 |
Good round-trip deal | $279 or less |
Good one-way deal | $74 or less |
Cheapflights Fare Finder
Customize your flight search to find flights from Colorado 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 May 13, 2026.
Use the filters below to find and compare flights from Colorado to Illinois that are best for you.
Fly from
Fly to
Route
Depart
Return
Cheapest round-trip
DenverChicago
DEN - ORD
DENORD
Denver Intl
Wed 7/8
6:00 pm-9:39 pm
Nonstop2h 39m
Chicago O'Hare Intl
Tue 7/14
5:00 am-6:41 am
Nonstop2h 41m
$217
DenverChicago
DEN - ORD
DENORD
Denver Intl
Thu 6/4
6:05 am-1:01 pm
1 stop5h 56m
Chicago O'Hare Intl
Mon 6/8
3:22 pm-9:57 pm
1 stop7h 35m
$241
Quickest round-trip
DenverChicago
DEN - MDW
DENMDW
Denver Intl
Mon 7/27
5:55 am-9:20 am
Nonstop2h 25m
Chicago Midway
Tue 7/28
5:30 am-7:05 am
Nonstop2h 35m
$241
DenverChicago
DEN - ORD
DENORD
Denver Intl
Sun 6/14
9:05 pm-12:44 am
Nonstop2h 39m
Chicago O'Hare Intl
Tue 6/16
6:00 am-7:42 am
Nonstop2h 42m
$241
DenverChicago
DEN - MDW
DENMDW
Denver Intl
Tue 7/7
6:15 am-9:40 am
Nonstop2h 25m
Chicago Midway
Thu 7/9
5:15 am-6:50 am
Nonstop2h 35m
$241
DenverChicago
DEN - MDW
DENMDW
Denver Intl
Thu 6/4
6:05 am-12:42 pm
1 stop5h 37m
Chicago Midway
Tue 6/9
6:00 am-12:59 pm
1 stop7h 59m
$247
DenverChicago
DEN - MDW
DENMDW
Denver Intl
Fri 8/28
4:55 pm-8:15 pm
Nonstop2h 20m
Chicago Midway
Tue 9/1
8:20 am-12:20 pm
1 stop5h 00m
$247
DenverChicago
DEN - MDW
DENMDW
Denver Intl
Tue 6/23
6:15 am-9:40 am
Nonstop2h 25m
Chicago Midway
Sat 6/27
12:50 pm-4:35 pm
1 stop4h 45m
$247
DenverChicago
DEN - ORD
DENORD
Denver Intl
Fri 7/3
6:00 am-11:31 am
1 stop4h 31m
Chicago O'Hare Intl
Tue 7/7
3:22 pm-8:53 pm
1 stop6h 31m
$261
DenverChicago
DEN - MDW
DENMDW
Denver Intl
Fri 6/19
7:05 pm-1:00 am
1 stop4h 55m
Chicago Midway
Tue 6/23
9:05 pm-10:50 pm
Nonstop2h 45m
$261
Showing 1-10 of 60 resultsSorted by cheapest first
Best time to book a flight from Colorado to Illinois
Have a flexible travel schedule? Discover the best time to fly to Illinois from Colorado with our price prediction graph.
DEN-PIA
DEN-STL
DEN-ORD
DEN-MDW
COS-STL
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 Colorado to Illinois
USCO-USIL
DEN-PIA
DEN-STL
DEN-ORD
DEN-MDW
How far ahead should I book a flight from Colorado to Illinois?
To ensure you get the cheapest price possible for a flight from Colorado to Illinois, you should look to book at least 78 days in advance of your intended travel date. The price of your flight may increase if you delay and leave booking until a week or so before departure.
What is the cheapest month to book a flight from Colorado to Illinois?
Currently, August is the cheapest month in which you can book a flight from Colorado to Illinois (average of $217). Flying from Colorado to Illinois in December is currently the most expensive (average of $387). 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 CO to IL?
Find hourly flight availability from Colorado 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 May 13, 2026.
A simple way to save on the total cost of your ticket is to fly from Colorado to Illinois in the evening. If you’re flexible enough to do this you can expect to save up to 36% on your trip compared to booking a flight at noon.
What is the cheapest day to fly from Colorado to Illinois?
Use this chart to determine the cheapest time to fly round-trip from Colorado to Illinois. Price data was last updated on May 9, 2026.
Travelers seeking maximum savings on their Colorado to Illinois flight should consider departing on Friday at noon when fares are most often at their lowest. Sunday afternoons flights should be avoided if possible as fares are typically the most expensive at this time.
Weekly flight availability from Colorado to Illinois
Explore weekly flight availability from Colorado to Illinois. Discover flights operating on different days of the week, giving you the flexibility to choose a travel day that best fits your plans. Compare info to find the most convenient option for your journey. Data last updated May 13, 2026.
The most flights from USCO to USIL are scheduled on a Tuesday (69 on average). You will have fewer flight options on Saturday, which is when the least amount of flights are scheduled (54 on average).
How much does it cost to fly round-trip from Colorado 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 May 13, 2026.
Read reviews from past customers who have flown Southwest,United Airlines, andAllegiant Air from Colorado to Illinois. You can also see how each airline compares in terms of entertainment options, comfort, food, crew/service, and boarding process.
Overall
7.9
Entertainment
7.5
Crew
8.6
Food
7.0
Boarding
8.1
Comfort
8.0
Reviews
1 / 20
2.0
MediocreDominic,Mar 2026
MCO - SMF
Overall
7.9
Entertainment
7.5
Crew
8.6
Food
7.0
Boarding
8.1
Comfort
8.0
Reviews
1 / 20
2.0
MediocreDominic,Mar 2026
MCO - SMF
Overall
7.9
Entertainment
7.5
Crew
8.6
Food
7.0
Boarding
8.1
Comfort
8.0
Reviews
1 / 20
2.0
MediocreDominic,Mar 2026
MCO - SMF
Overall
7.9
Entertainment
7.5
Crew
8.6
Food
7.0
Boarding
8.1
Comfort
8.0
Reviews
1 / 20
2.0
MediocreDominic,Mar 2026
MCO - SMF
Overall
7.9
Entertainment
7.5
Crew
8.6
Food
7.0
Boarding
8.1
Comfort
8.0
Reviews
1 / 20
2.0
MediocreDominic,Mar 2026
MCO - SMF
Overall
7.9
Entertainment
7.5
Crew
8.6
Food
7.0
Boarding
8.1
Comfort
8.0
Reviews
1 / 20
2.0
MediocreDominic,Mar 2026
MCO - SMF
Related info for your journey
Find useful and relevant information for your journey from Colorado 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 Colorado 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 Colorado to Illinois by cabin class
Find flights from Colorado to Illinois, based on your preferred cabin class, be it economy, premium economy, business, or first class.
Colorado and Illinois flights
Browse other Colorado and Illinois flight options. Last updated on May 13, 2026.
Popular flight searches
Check out other popular destinations found by fellow travelers in 2026
Find a return flight route from Illinois
Find the right flight back to Colorado after your stay in Illinois
Colorado to Illinois flights
Consider these flights traveling from Colorado to Illinois.
Top 6 airlines flying from Colorado to Illinois
Discover the top 6 airlines that operate flights from Colorado 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 May 13, 2026.
| Airline | Cheapest | Average | Flexibility | On-time |
|---|---|---|---|---|
| Cheapest$76 | Average$186 | FlexibilityNo cancel fee | On-time62% | |
| Cheapest$84 | Average$168 | FlexibilityNo cancel fee | On-time88% | |
| Cheapest$126 | Average$191 | FlexibilityNo cancel fee | On-time62% | |
| Cheapest$157 | Average$315 | FlexibilityNo cancel fee | On-time63% | |
| Cheapest$159 | Average$425 | FlexibilityNo cancel fee | On-time71% | |
| Cheapest$170 | Average$432 | FlexibilityNo cancel fee | On-time69% |