$27+ 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 4/18. Fares are subject to change and may not be available on all flights or dates of travel.
DEN — ORD
Mar 16 — Mar 231
1 adult, Economy
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Find cheap flights from Colorado to Illinois with Cheapflights
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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 February 14, 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 February 14, 2026.
This Super.com deal was found by Cheapflights users on 2/10. 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 Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 3/76:35 am
DEN
- STL
Nonstop2h 14m
Frontier
Sat 3/78:12 pm
STL
- DEN
Nonstop2h 37m
Frontier
Deal found 2/10![Frontier logo]()
$85
This Kiwi.com deal was found by Cheapflights users on 2/11. 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.
Fri 5/84:00 pm
DEN
- STL
Nonstop2h 12m
Frontier
Sun 5/108:12 pm
STL
- DEN
Nonstop2h 33m
Frontier
Deal found 2/11![Frontier logo]()
$87
This Kiwi.com deal was found by Cheapflights users on 2/10. 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 3/412:48 pm
DEN
- STL
Nonstop2h 05m
Frontier
Fri 3/68:12 pm
STL
- DEN
Nonstop2h 37m
Frontier
Deal found 2/10![Frontier logo]()
$97
This Super.com deal was found by Cheapflights users on 2/12. 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.
Mon 3/236:35 am
DEN
- STL
Nonstop2h 14m
Frontier
Fri 3/278:12 pm
STL
- DEN
Nonstop2h 37m
Frontier
Deal found 2/12![Frontier logo]()
$106
This Frontier deal was found by Cheapflights users on 2/11. 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.
Sat 4/184:00 pm
DEN
- STL
Nonstop2h 12m
Frontier
Sun 4/1911:21 am
STL
- DEN
1 stop12h 42m
Frontier
Deal found 2/11![Frontier logo]()
$108
This Frontier deal was found by Cheapflights users on 2/12. 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 4/66:40 am
DEN
- STL
Nonstop2h 08m
Frontier
Sat 4/118:16 pm
STL
- DEN
Nonstop2h 33m
Frontier
Deal found 2/12![Frontier logo]()
$112
This Cheapflightsfares deal was found by Cheapflights users on 2/14. 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 Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 3/116:35 am
DEN
- STL
Nonstop2h 14m
Frontier
Wed 3/1811:32 am
STL
- DEN
1 stop12h 32m
Frontier
Deal found 2/14![Frontier logo]()
$113
This Priceline deal was found by Cheapflights users on 2/11. 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 Priceline is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 3/1711:59 pm
DEN
- STL
1 stop9h 38m
Frontier
Wed 3/188:12 pm
STL
- DEN
Nonstop2h 37m
Frontier
Deal found 2/11![Frontier logo]()
$114
This Frontier deal was found by Cheapflights users on 2/11. 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.
Wed 4/810:45 am
DEN
- ORD
Nonstop2h 34m
Frontier
Fri 4/102:29 pm
ORD
- DEN
Nonstop3h 11m
Frontier
Deal found 2/11![Frontier logo]()
$135
This Kiwi.com deal was found by Cheapflights users on 2/10. 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.
Thu 3/57:35 pm
DEN
- ORD
Nonstop2h 39m
Multiple Airlines
Mon 3/96:51 pm
ORD
- DEN
2 stops18h 08m
Multiple Airlines
Deal found 2/10![Multiple Airlines logo]()
$136
This Kiwi.com deal was found by Cheapflights users on 2/10. 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.
Thu 3/512:42 pm
DEN
- MDW
1 stop7h 30m
Frontier
Mon 3/96:05 am
MDW
- DEN
1 stop30h 54m
Frontier
Deal found 2/10![Frontier logo]()
$136
This Kiwi.com deal was found by Cheapflights users on 2/13. 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.
Sun 3/86:00 am
DEN
- ORD
Nonstop2h 43m
Multiple Airlines
Mon 3/164:51 pm
ORD
- DEN
1 stop16h 35m
Multiple Airlines
Deal found 2/13![Multiple Airlines logo]()
$137
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 February 14, 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 February 14, 2026.
This Super.com deal was found by Cheapflights users on 2/10. 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 Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 3/76:35 am
DEN
- STL
Nonstop2h 14m
Frontier
Sat 3/71:58 pm
STL
- DEN
1 stop10h 10m
Frontier
Deal found 2/10![Frontier logo]()
$141
This United Airlines deal was found by Cheapflights users on 2/13. 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 3/217:25 pm
DEN
- ORD
Nonstop2h 30m
United Airlines
Tue 3/247:57 pm
ORD
- DEN
Nonstop2h 58m
United Airlines
Deal found 2/13![United Airlines logo]()
$154
This Southwest deal was found by Cheapflights users on 2/10. 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.
Tue 4/285:55 pm
DEN
- MDW
Nonstop2h 35m
Southwest
Mon 5/45:15 pm
MDW
- DEN
Nonstop2h 40m
Southwest
Deal found 2/10![Southwest logo]()
$187
This Delta deal was found by Cheapflights users on 2/10. 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.
Wed 4/157:59 am
COS
- STL
1 stop8h 27m
Delta
Tue 4/217:25 am
STL
- COS
1 stop5h 52m
Delta
Deal found 2/10![Delta logo]()
$199
This American Airlines deal was found by Cheapflights users on 2/10. 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 American Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 4/286:11 am
DEN
- STL
1 stop4h 34m
American Airlines
Wed 4/296:11 pm
STL
- DEN
1 stop6h 34m
American Airlines
Deal found 2/10![American Airlines logo]()
$199
This Kiwi.com deal was found by Cheapflights users on 2/10. 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.
Thu 6/44:24 pm
DEN
- PIA
Nonstop2h 06m
Allegiant Air
Sun 6/711:07 am
PIA
- DEN
Nonstop2h 27m
Allegiant Air
Deal found 2/10![Allegiant Air logo]()
$205
This Cheapflightsfares deal was found by Cheapflights users on 2/10. 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.
Tue 2/249:25 am
DEN
- STL
1 stop12h 02m
Frontier
Wed 2/254:51 pm
STL
- DEN
Nonstop2h 34m
Frontier
Deal found 2/10![Frontier logo]()
$164
This United Airlines deal was found by Cheapflights users on 2/10. 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.
Tue 5/55:34 pm
DEN
- STL
Nonstop2h 09m
United Airlines
Tue 5/124:06 pm
STL
- DEN
Nonstop2h 34m
United Airlines
Deal found 2/10![United Airlines logo]()
$179
This Southwest deal was found by Cheapflights users on 2/10. 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.
Tue 3/36:25 pm
DEN
- MDW
Nonstop2h 25m
Southwest
Sat 3/76:20 pm
MDW
- DEN
Nonstop2h 45m
Southwest
Deal found 2/10![Southwest logo]()
$187
This United Airlines deal was found by Cheapflights users on 2/10. 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.
Tue 3/108:20 pm
DEN
- STL
Nonstop2h 14m
United Airlines
Tue 3/175:15 am
STL
- DEN
Nonstop2h 40m
United Airlines
Deal found 2/10![United Airlines logo]()
$179
This Delta deal was found by Cheapflights users on 2/10. 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.
Wed 4/227:59 am
COS
- STL
1 stop8h 27m
Delta
Tue 4/286:00 am
STL
- COS
1 stop7h 17m
Delta
Deal found 2/10![Delta logo]()
$199
This American Airlines deal was found by Cheapflights users on 2/13. 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 American Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 5/146:11 am
DEN
- ORD
Nonstop2h 36m
American Airlines
Sun 5/176:05 am
ORD
- DEN
1 stop8h 44m
American Airlines
Deal found 2/13![American Airlines logo]()
$201
This Southwest deal was found by Cheapflights users on 2/10. 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 3/57:30 pm
DEN
- MDW
Nonstop2h 20m
Southwest
Mon 3/93:00 pm
MDW
- DEN
Nonstop2h 40m
Southwest
Deal found 2/10![Southwest logo]()
$193
This Delta deal was found by Cheapflights users on 2/13. 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 Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 4/286:25 pm
DEN
- STL
1 stop5h 00m
Delta
Wed 4/297:25 am
STL
- DEN
1 stop8h 52m
Delta
Deal found 2/13![Delta logo]()
$199
This United Airlines deal was found by Cheapflights users on 2/10. 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.
Tue 3/37:23 pm
DEN
- ORD
Nonstop2h 29m
United Airlines
Sat 3/79:39 pm
ORD
- DEN
Nonstop2h 51m
United Airlines
Deal found 2/10![United Airlines logo]()
$187
This Kiwi.com deal was found by Cheapflights users on 2/11. 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.
Thu 5/214:27 pm
DEN
- PIA
Nonstop2h 03m
Allegiant Air
Sun 5/245:13 pm
PIA
- DEN
Nonstop2h 23m
Allegiant Air
Deal found 2/11![Allegiant Air logo]()
$227
This Southwest deal was found by Cheapflights users on 2/13. 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.
Tue 4/216:35 am
DEN
- MDW
Nonstop2h 20m
Southwest
Thu 4/235:30 am
MDW
- DEN
1 stop5h 45m
Southwest
Deal found 2/13![Southwest logo]()
$197
This Delta deal was found by Cheapflights users on 2/13. 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 Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 3/2012:35 am
DEN
- MDW
1 stop7h 18m
Delta
Tue 3/247:20 pm
MDW
- DEN
1 stop5h 19m
Delta
Deal found 2/13![Delta logo]()
$201
This United Airlines deal was found by Cheapflights users on 2/10. 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.
Tue 3/178:20 pm
DEN
- STL
Nonstop2h 14m
United Airlines
Thu 3/196:02 pm
STL
- DEN
Nonstop2h 35m
United Airlines
Deal found 2/10![United Airlines logo]()
$187
This American Airlines deal was found by Cheapflights users on 2/12. 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.
Tue 3/35:50 am
DRO
- ORD
1 stop6h 14m
American Airlines
Mon 3/95:00 am
ORD
- DRO
1 stop7h 04m
American Airlines
Deal found 2/12![American Airlines logo]()
$228
This Southwest deal was found by Cheapflights users on 2/10. 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 4/2312:40 pm
DEN
- MDW
1 stop4h 20m
Southwest
Sun 4/266:00 am
MDW
- DEN
Nonstop2h 40m
Southwest
Deal found 2/10![Southwest logo]()
$201
This Delta deal was found by Cheapflights users on 2/10. 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 4/236:25 pm
DEN
- STL
1 stop5h 00m
Delta
Sat 4/257:02 am
STL
- DEN
1 stop5h 30m
Delta
Deal found 2/10![Delta logo]()
$201
This American Airlines deal was found by Cheapflights users on 2/12. 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 4/176:11 am
DEN
- PIA
1 stop5h 41m
American Airlines
Mon 4/207:05 pm
PIA
- DEN
1 stop5h 54m
American Airlines
Deal found 2/12![American Airlines logo]()
$229
This United Airlines deal was found by Cheapflights users on 2/11. 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.
Thu 4/96:00 am
DEN
- ORD
Nonstop2h 37m
United Airlines
Mon 4/138:06 pm
ORD
- DEN
Nonstop2h 59m
United Airlines
Deal found 2/11![United Airlines logo]()
$195
This Southwest deal was found by Cheapflights users on 2/12. 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.
Wed 4/156:15 am
DEN
- ORD
1 stop6h 00m
Southwest
Wed 4/152:40 pm
ORD
- DEN
2 stops8h 25m
Southwest
Deal found 2/12![Southwest logo]()
$204
This Delta deal was found by Cheapflights users on 2/13. 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 Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 3/236:10 am
DEN
- MDW
1 stop5h 19m
Delta
Tue 3/247:20 pm
MDW
- DEN
1 stop5h 19m
Delta
Deal found 2/13![Delta logo]()
$207
This United Airlines deal was found by Cheapflights users on 2/10. 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.
Thu 3/54:25 pm
DEN
- ORD
Nonstop2h 35m
United Airlines
Sat 3/75:50 pm
ORD
- DEN
Nonstop2h 58m
United Airlines
Deal found 2/10![United Airlines logo]()
$195
This Southwest deal was found by Cheapflights users on 2/12. 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.
Wed 3/255:05 am
DEN
- ORD
1 stop6h 45m
Southwest
Wed 3/252:40 pm
ORD
- DEN
2 stops9h 15m
Southwest
Deal found 2/12![Southwest logo]()
$204
This Delta deal was found by Cheapflights users on 2/11. 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.
Wed 4/812:35 am
DEN
- MDW
1 stop7h 18m
Delta
Tue 4/1410:43 am
MDW
- DEN
1 stop7h 12m
Delta
Deal found 2/11![Delta logo]()
$207
This United Airlines deal was found by Cheapflights users on 2/10. 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.
Wed 4/2210:28 am
COS
- STL
1 stop5h 28m
United Airlines
Tue 4/284:30 pm
STL
- COS
1 stop5h 16m
United Airlines
Deal found 2/10![United Airlines logo]()
$199
Last-minute flights from Colorado to IllinoisDiscover last-minute flight deals from Colorado to Illinois. Data last updated February 14, 2026 and is based on user searches.
Discover last-minute flight deals from Colorado to Illinois. Data last updated February 14, 2026 and is based on user searches.
This Kiwi.com deal was found by Cheapflights users on 2/10. 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 3/412:48 pm
DEN
- STL
Nonstop2h 05m
Frontier
Fri 3/68:12 pm
STL
- DEN
Nonstop2h 37m
Frontier
Deal found 2/10![Frontier logo]()
$97
This Kiwi.com deal was found by Cheapflights users on 2/10. 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.
Thu 3/56:00 am
DEN
- ORD
1 stop7h 54m
Frontier
Thu 3/1210:53 am
ORD
- DEN
Nonstop2h 59m
Frontier
Deal found 2/10![Frontier logo]()
$135
This Kiwi.com deal was found by Cheapflights users on 2/10. 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.
Thu 3/57:35 pm
DEN
- ORD
Nonstop2h 39m
Multiple Airlines
Mon 3/96:51 pm
ORD
- DEN
2 stops18h 08m
Multiple Airlines
Deal found 2/10![Multiple Airlines logo]()
$136
This Super.com deal was found by Cheapflights users on 2/10. 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 Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 3/76:35 am
DEN
- STL
Nonstop2h 14m
Frontier
Sat 3/78:12 pm
STL
- DEN
Nonstop2h 37m
Frontier
Deal found 2/10![Frontier logo]()
$85
This Expedia deal was found by Cheapflights users on 2/14. 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 Expedia is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 3/96:35 am
DEN
- STL
Nonstop2h 14m
Frontier
Wed 3/1111:32 am
STL
- DEN
1 stop12h 32m
Frontier
Deal found 2/14![Frontier logo]()
$123
This Cheapflightsfares deal was found by Cheapflights users on 2/14. 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 Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 3/116:35 am
DEN
- STL
Nonstop2h 14m
Frontier
Wed 3/1811:32 am
STL
- DEN
1 stop12h 32m
Frontier
Deal found 2/14![Frontier logo]()
$113
This Kiwi.com deal was found by Cheapflights users on 2/14. 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.
Wed 3/116:35 am
DEN
- STL
Nonstop2h 14m
Frontier
Fri 3/138:12 pm
STL
- DEN
Nonstop2h 37m
Frontier
Deal found 2/14![Frontier logo]()
$117
This Kiwi.com deal was found by Cheapflights users on 2/14. 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.
Fri 3/136:35 am
DEN
- STL
Nonstop2h 14m
Frontier
Mon 3/168:12 pm
STL
- DEN
Nonstop2h 37m
Frontier
Deal found 2/14![Frontier logo]()
$111
This Cheapflightsfares deal was found by Cheapflights users on 2/10. 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.
Mon 3/166:35 am
DEN
- STL
Nonstop2h 14m
Frontier
Wed 3/1811:32 am
STL
- DEN
1 stop12h 32m
Frontier
Deal found 2/10![Frontier logo]()
$122
This Priceline deal was found by Cheapflights users on 2/11. 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 Priceline is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 3/1711:59 pm
DEN
- STL
1 stop9h 38m
Frontier
Wed 3/188:12 pm
STL
- DEN
Nonstop2h 37m
Frontier
Deal found 2/11![Frontier logo]()
$114
This Super.com deal was found by Cheapflights users on 2/12. 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.
Mon 3/236:35 am
DEN
- STL
Nonstop2h 14m
Frontier
Fri 3/278:12 pm
STL
- DEN
Nonstop2h 37m
Frontier
Deal found 2/12![Frontier logo]()
$106
This Super.com deal was found by Cheapflights users on 2/12. 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.
Fri 3/276:35 am
DEN
- STL
Nonstop2h 14m
Frontier
Fri 4/38:16 pm
STL
- DEN
Nonstop2h 33m
Frontier
Deal found 2/12![Frontier logo]()
$126
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 February 14, 2026.
Search for one-way flight options from Colorado to Illinois. Find affordable one-way fares based on user searches. Data last updated February 14, 2026.
This Kiwi.com deal was found by Cheapflights users on 2/11. 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.
Sat 4/184:00 pm
DEN
- STL
Nonstop2h 12m
Frontier
Deal found 2/11![Frontier logo]()
$27
This Kiwi.com deal was found by Cheapflights users on 2/11. 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 3/412:48 pm
DEN
- STL
Nonstop2h 05m
Frontier
Deal found 2/11![Frontier logo]()
$33
This Super.com deal was found by Cheapflights users on 2/10. 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 Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 3/186:35 am
DEN
- STL
Nonstop2h 14m
Frontier
Deal found 2/10![Frontier logo]()
$34
This Kiwi.com deal was found by Cheapflights users on 2/10. 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.
Mon 4/204:00 pm
DEN
- STL
Nonstop2h 12m
Frontier
Deal found 2/10![Frontier logo]()
$42
This Priceline deal was found by Cheapflights users on 2/11. 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 Priceline is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 3/166:35 am
DEN
- STL
Nonstop2h 14m
Frontier
Deal found 2/11![Frontier logo]()
$43
This Expedia deal was found by Cheapflights users on 2/14. 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 Expedia is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 4/244:00 pm
DEN
- STL
Nonstop2h 12m
Frontier
Deal found 2/14![Frontier logo]()
$44
This Kiwi.com deal was found by Cheapflights users on 2/14. 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.
Fri 5/154:00 pm
DEN
- STL
Nonstop2h 12m
Frontier
Deal found 2/14![Frontier logo]()
$52
This Kiwi.com deal was found by Cheapflights users on 2/11. 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.
Sat 3/286:35 am
DEN
- STL
Nonstop2h 14m
Frontier
Deal found 2/11![Frontier logo]()
$60
This Kiwi.com deal was found by Cheapflights users on 2/12. 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.
Fri 4/36:40 am
DEN
- STL
Nonstop2h 08m
Frontier
Deal found 2/12![Frontier logo]()
$63
This Cheapflightsfares deal was found by Cheapflights users on 2/14. 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 Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 3/276:35 am
DEN
- STL
Nonstop2h 14m
Frontier
Deal found 2/14![Frontier logo]()
$64
This United Airlines deal was found by Cheapflights users on 2/14. 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.
Sat 4/45:45 pm
DEN
- STL
Nonstop2h 09m
United Airlines
Deal found 2/14![United Airlines logo]()
$65
This Cheapflightsfares deal was found by Cheapflights users on 2/14. 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 Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 2/279:41 am
DEN
- ORD
Nonstop2h 44m
Frontier
Deal found 2/14![Frontier logo]()
$84
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 February 14, 2026.
Most accurate provider | FlightHub 3 stars |
|---|---|
Most trusted provider | FlightHub 3 stars |
Round-trip from | $85 (Super.com) |
One-way from | $27 (Kiwi.com) |
Popular in | November |
Cheapest in | August |
Average price | $218 |
Good round-trip deal | $251 or less |
Good one-way deal | $133 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 February 14, 2026.
Use the filters below to find and compare flights from Colorado to Illinois that are best for you.
Fly from
Colorado
Fly to
Illinois
Route
Depart
Return
Price
DenverSt. Louis
DEN - STL
DENSTL
Denver Intl
Sat 3/7
6:35 am-9:49 am
Nonstop2h 14m
Lambert-St Louis
Sat 3/7
1:58 pm-11:08 pm
1 stop10h 10m
$141
DenverChicago
DEN - ORD
DENORD
Denver Intl
Sat 3/21
7:25 pm-10:55 pm
Nonstop2h 30m
Chicago O'Hare Intl
Tue 3/24
7:57 pm-9:55 pm
Nonstop2h 58m
$154
DenverSt. Louis
DEN - STL
DENSTL
Denver Intl
Tue 2/24
9:25 am-10:27 pm
1 stop12h 02m
Lambert-St Louis
Wed 2/25
4:51 pm-6:25 pm
Nonstop2h 34m
$164
DenverSt. Louis
DEN - STL
DENSTL
Denver Intl
Tue 5/5
5:34 pm-8:43 pm
Nonstop2h 09m
Lambert-St Louis
Tue 5/12
4:06 pm-5:40 pm
Nonstop2h 34m
$179
DenverSt. Louis
DEN - STL
DENSTL
Denver Intl
Tue 3/10
8:20 pm-11:34 pm
Nonstop2h 14m
Lambert-St Louis
Tue 3/17
5:15 am-6:55 am
Nonstop2h 40m
$179
DenverChicago
DEN - MDW
DENMDW
Denver Intl
Tue 4/28
5:55 pm-9:30 pm
Nonstop2h 35m
Chicago Midway
Mon 5/4
5:15 pm-6:55 pm
Nonstop2h 40m
$187
DenverChicago
DEN - MDW
DENMDW
Denver Intl
Tue 3/3
6:25 pm-9:50 pm
Nonstop2h 25m
Chicago Midway
Sat 3/7
6:20 pm-8:05 pm
Nonstop2h 45m
$187
DenverChicago
DEN - ORD
DENORD
Denver Intl
Tue 3/3
7:23 pm-10:52 pm
Nonstop2h 29m
Chicago O'Hare Intl
Sat 3/7
9:39 pm-11:30 pm
Nonstop2h 51m
$187
DenverSt. Louis
DEN - STL
DENSTL
Denver Intl
Tue 3/17
8:20 pm-11:34 pm
Nonstop2h 14m
Lambert-St Louis
Thu 3/19
6:02 pm-7:37 pm
Nonstop2h 35m
$187
DenverChicago
DEN - MDW
DENMDW
Denver Intl
Thu 3/5
7:30 pm-10:50 pm
Nonstop2h 20m
Chicago Midway
Mon 3/9
3:00 pm-4:40 pm
Nonstop2h 40m
$193
Showing 1-10 of 60 results
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-STL
DEN-MDW
COS-STL
EGE-ORD
COS-ORD
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-STL
DEN-MDW
COS-STL
EGE-ORD
What is the cheapest month to book a flight from Colorado to Illinois?
Currently, July is the cheapest month in which you can book a flight from Colorado to Illinois (average of $46). Flying from Colorado to Illinois in June is currently the most expensive (average of $109). 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 February 14, 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 42% 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 February 7, 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 February 14, 2026.
The most flights from USCO to USIL are scheduled on a Friday (60 on average). You will have fewer flight options on Saturday, which is when the least amount of flights are scheduled (33 on average).
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 February 14, 2026.
Read reviews from past customers who have flown Southwest, United Airlines, and American Airlines from Colorado to Illinois. You can also see how each airline compares in terms of entertainment options, comfort, food, crew/service, and boarding process.
Boarding
8.1
Overall
8.0
Crew
8.6
Comfort
8.0
Entertainment
7.5
Food
7.0
Reviews
1 / 20
2.0
MediocreThomas,Dec 2025
SEA - DEN
Boarding
8.1
Overall
8.0
Crew
8.6
Comfort
8.0
Entertainment
7.5
Food
7.0
Reviews
1 / 20
2.0
MediocreThomas,Dec 2025
SEA - DEN
Boarding
8.1
Overall
8.0
Crew
8.6
Comfort
8.0
Entertainment
7.5
Food
7.0
Reviews
1 / 20
2.0
MediocreThomas,Dec 2025
SEA - DEN
Boarding
8.1
Overall
8.0
Crew
8.6
Comfort
8.0
Entertainment
7.5
Food
7.0
Reviews
1 / 20
2.0
MediocreThomas,Dec 2025
SEA - DEN
Boarding
8.1
Overall
8.0
Crew
8.6
Comfort
8.0
Entertainment
7.5
Food
7.0
Reviews
1 / 20
2.0
MediocreThomas,Dec 2025
SEA - DEN
Boarding
8.1
Overall
8.0
Crew
8.6
Comfort
8.0
Entertainment
7.5
Food
7.0
Reviews
1 / 20
2.0
MediocreThomas,Dec 2025
SEA - DEN
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.
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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 February 14, 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 February 14, 2026.
| Airline | Cheapest | Average | Flexibility | On-time |
|---|---|---|---|---|
| Cheapest$63 | Average$179 | FlexibilityNo cancel fee | On-time62% | |
| Cheapest$68 | Average$142 | FlexibilityNo cancel fee | On-time88% | |
| Cheapest$126 | Average$191 | FlexibilityNo cancel fee | On-time62% | |
| Cheapest$155 | Average$288 | FlexibilityNo cancel fee | On-time63% | |
| Cheapest$157 | Average$451 | FlexibilityNo cancel fee | On-time71% | |
| Cheapest$158 | Average$432 | FlexibilityNo cancel fee | On-time69% |