$94+ 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 9/23. Fares are subject to change and may not be available on all flights or dates of travel.
DEN — ORD
Aug 16 — Aug 231
Round-trip
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 July 17, 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 July 17, 2026.
This Mytrip deal was found by Cheapflights users on 7/12. 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 Mytrip is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sun 9/272:26 pm
DEN
- PIA
Nonstop2h 03m
Allegiant Air
Sun 10/45:24 pm
PIA
- DEN
Nonstop2h 20m
Allegiant Air
Deal found 7/12![Allegiant Air logo]()
$136
This Cheapflightsfares deal was found by Cheapflights users on 7/15. 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 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 8/3010:07 am
PIA
- DEN
Nonstop2h 19m
Allegiant Air
Deal found 7/15![Allegiant Air logo]()
$146
This Cheapflightsfares deal was found by Cheapflights users on 7/12. 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.
Thu 8/134:27 pm
DEN
- PIA
Nonstop2h 10m
Allegiant Air
Sun 8/2310:07 am
PIA
- DEN
Nonstop2h 19m
Allegiant Air
Deal found 7/12![Allegiant Air logo]()
$154
This Super.com deal was found by Cheapflights users on 7/15. 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 Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 8/45:05 pm
DEN
- ORD
Nonstop2h 47m
Frontier
Tue 8/119:57 pm
ORD
- DEN
Nonstop3h 00m
Frontier
Deal found 7/15![Frontier logo]()
$174
This Kiwi.com deal was found by Cheapflights users on 7/13. 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 8/45:05 pm
DEN
- ORD
Nonstop2h 47m
Frontier
Fri 8/79:57 pm
ORD
- DEN
Nonstop3h 00m
Frontier
Deal found 7/13![Frontier logo]()
$175
This Frontier deal was found by Cheapflights users on 7/13. 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.
Fri 8/75:05 pm
DEN
- ORD
Nonstop2h 47m
Frontier
Wed 8/192:41 pm
ORD
- DEN
Nonstop3h 04m
Frontier
Deal found 7/13![Frontier logo]()
$176
This Kiwi.com deal was found by Cheapflights users on 7/16. 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 Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 8/272:17 pm
DEN
- PIA
Nonstop2h 07m
Allegiant Air
Sun 9/610:07 am
PIA
- DEN
Nonstop2h 20m
Allegiant Air
Deal found 7/16![Allegiant Air logo]()
$176
This Trip.com deal was found by Cheapflights users on 7/16. 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 Trip.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 8/85:05 pm
DEN
- ORD
Nonstop2h 47m
Frontier
Mon 8/109:57 pm
ORD
- DEN
Nonstop3h 00m
Frontier
Deal found 7/16![Frontier logo]()
$177
This Kiwi.com deal was found by Cheapflights users on 7/16. 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 Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 9/108:40 am
DEN
- ORD
2 stops10h 04m
Frontier
Mon 9/1411:06 am
ORD
- DEN
Nonstop2h 54m
Frontier
Deal found 7/16![Frontier logo]()
$178
This Kiwi.com deal was found by Cheapflights users on 7/16. 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 Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 8/118:52 pm
DEN
- ORD
2 stops46h 01m
Frontier
Tue 8/182:41 pm
ORD
- DEN
Nonstop3h 04m
Frontier
Deal found 7/16![Frontier logo]()
$179
This Super.com deal was found by Cheapflights users on 7/16. 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.
Wed 8/269:55 am
DEN
- ORD
Nonstop2h 41m
Frontier
Sun 8/302:41 pm
ORD
- DEN
Nonstop3h 04m
Frontier
Deal found 7/16![Frontier logo]()
$180
This Frontier deal was found by Cheapflights users on 7/13. 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.
Wed 8/125:05 pm
DEN
- ORD
Nonstop2h 47m
Frontier
Mon 8/179:57 pm
ORD
- DEN
Nonstop3h 00m
Frontier
Deal found 7/13![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 July 17, 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 July 17, 2026.
This United Airlines deal was found by Cheapflights users on 7/14. 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.
Thu 8/205:35 pm
DEN
- STL
Nonstop2h 11m
United Airlines
Tue 8/251:36 pm
STL
- DEN
Nonstop2h 24m
United Airlines
Deal found 7/14![United Airlines logo]()
$187
This Southwest deal was found by Cheapflights users on 7/15. 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.
Sat 8/2911:15 am
DEN
- STL
1 stop3h 15m
Southwest
Sat 9/52:25 pm
STL
- DEN
1 stop5h 15m
Southwest
Deal found 7/15![Southwest logo]()
$202
This Delta deal was found by Cheapflights users on 7/12. 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 Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 10/710:45 am
DEN
- STL
1 stop5h 49m
Delta
Tue 10/1310:15 am
STL
- DEN
1 stop7h 53m
Delta
Deal found 7/12![Delta logo]()
$207
This United Airlines deal was found by Cheapflights users on 7/16. 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.
Sat 8/159:35 am
DEN
- STL
Nonstop2h 05m
United Airlines
Sat 8/228:30 am
STL
- DEN
1 stop7h 01m
United Airlines
Deal found 7/16![United Airlines logo]()
$197
This Southwest deal was found by Cheapflights users on 7/15. 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.
Tue 10/67:00 am
DEN
- MDW
Nonstop2h 20m
Southwest
Thu 10/86:05 am
MDW
- DEN
Nonstop2h 40m
Southwest
Deal found 7/15![Southwest logo]()
$205
This Delta deal was found by Cheapflights users on 7/16. 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.
Wed 9/26:00 am
DEN
- STL
1 stop7h 33m
Delta
Wed 9/95:46 pm
STL
- DEN
1 stop6h 09m
Delta
Deal found 7/16![Delta logo]()
$207
This American Airlines deal was found by Cheapflights users on 7/13. 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.
Wed 10/712:48 pm
ASE
- ORD
Nonstop3h 17m
American Airlines
Sun 10/112:50 pm
ORD
- ASE
1 stop6h 31m
American Airlines
Deal found 7/13![American Airlines logo]()
$416
This United Airlines deal was found by Cheapflights users on 7/11. 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 8/69:05 pm
DEN
- ORD
Nonstop2h 39m
United Airlines
Mon 8/106:00 am
ORD
- DEN
Nonstop2h 42m
United Airlines
Deal found 7/11![United Airlines logo]()
$205
This Southwest deal was found by Cheapflights users on 7/16. 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 Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 8/2211:10 am
DEN
- MDW
1 stop5h 00m
Southwest
Tue 8/2512:00 pm
MDW
- DEN
Nonstop2h 30m
Southwest
Deal found 7/16![Southwest logo]()
$211
This Delta deal was found by Cheapflights users on 7/14. 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.
Wed 8/1912:59 am
DEN
- ORD
1 stop5h 57m
Delta
Thu 8/205:20 pm
ORD
- DEN
1 stop6h 28m
Delta
Deal found 7/14![Delta logo]()
$225
This United Airlines deal was found by Cheapflights users on 7/14. 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.
Tue 8/118:29 pm
DEN
- ORD
Nonstop2h 30m
United Airlines
Thu 8/1310:00 pm
ORD
- DEN
Nonstop2h 53m
United Airlines
Deal found 7/14![United Airlines logo]()
$205
This Southwest deal was found by Cheapflights users on 7/14. 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 Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 9/148:25 pm
DEN
- MDW
Nonstop2h 20m
Southwest
Thu 9/1710:05 am
MDW
- DEN
1 stop5h 20m
Southwest
Deal found 7/14![Southwest logo]()
$215
This Delta deal was found by Cheapflights users on 7/13. 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.
Thu 10/2910:30 am
DEN
- ORD
1 stop4h 54m
Delta
Mon 11/27:10 am
ORD
- DEN
1 stop7h 58m
Delta
Deal found 7/13![Delta logo]()
$225
This United Airlines deal was found by Cheapflights users on 7/16. 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.
Thu 8/278:29 pm
DEN
- ORD
Nonstop2h 30m
United Airlines
Sat 8/297:50 pm
ORD
- DEN
Nonstop2h 54m
United Airlines
Deal found 7/16![United Airlines logo]()
$205
This Southwest deal was found by Cheapflights users on 7/16. 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 Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 10/312:30 pm
DEN
- MDW
1 stop4h 30m
Southwest
Mon 10/511:05 am
MDW
- DEN
1 stop5h 40m
Southwest
Deal found 7/16![Southwest logo]()
$220
This Delta deal was found by Cheapflights users on 7/13. 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.
Sun 10/2512:59 am
DEN
- ORD
1 stop6h 04m
Delta
Thu 10/296:30 am
ORD
- DEN
1 stop4h 27m
Delta
Deal found 7/13![Delta logo]()
$225
This Southwest deal was found by Cheapflights users on 7/15. 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.
Thu 9/35:00 am
DEN
- MDW
1 stop5h 00m
Southwest
Mon 9/76:20 am
MDW
- DEN
1 stop4h 00m
Southwest
Deal found 7/15![Southwest logo]()
$225
This Delta deal was found by Cheapflights users on 7/16. 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.
Fri 8/2112:59 am
DEN
- MDW
1 stop7h 18m
Delta
Tue 8/251:25 pm
MDW
- DEN
1 stop4h 58m
Delta
Deal found 7/16![Delta logo]()
$225
This Southwest deal was found by Cheapflights users on 7/12. 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.
Sat 8/2211:10 am
DEN
- MDW
2 stops7h 00m
Southwest
Mon 8/245:00 pm
MDW
- DEN
1 stop3h 50m
Southwest
Deal found 7/12![Southwest logo]()
$226
This Delta deal was found by Cheapflights users on 7/15. 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 Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 11/94:00 pm
DEN
- ORD
1 stop4h 34m
Delta
Tue 11/106:00 am
ORD
- DEN
1 stop5h 12m
Delta
Deal found 7/15![Delta logo]()
$235
This United Airlines deal was found by Cheapflights users on 7/14. 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.
Tue 8/45:34 pm
DEN
- STL
Nonstop2h 09m
United Airlines
Tue 8/251:36 pm
STL
- DEN
Nonstop2h 24m
United Airlines
Deal found 7/14![United Airlines logo]()
$267
This Southwest deal was found by Cheapflights users on 7/12. 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.
Sat 9/55:45 am
DEN
- MDW
2 stops6h 35m
Southwest
Mon 9/77:30 am
MDW
- DEN
1 stop5h 00m
Southwest
Deal found 7/12![Southwest logo]()
$230
This United Airlines deal was found by Cheapflights users on 7/16. 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.
Wed 9/29:35 am
DEN
- STL
Nonstop2h 05m
United Airlines
Wed 9/91:36 pm
STL
- DEN
Nonstop2h 24m
United Airlines
Deal found 7/16![United Airlines logo]()
$267
This Delta deal was found by Cheapflights users on 7/15. 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 Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sun 9/610:19 am
DEN
- ORD
1 stop4h 58m
Delta
Mon 9/145:50 pm
ORD
- DEN
1 stop6h 45m
Delta
Deal found 7/15![Delta logo]()
$255
This Southwest deal was found by Cheapflights users on 7/15. 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.
Sat 8/156:00 am
DEN
- MDW
Nonstop2h 20m
Southwest
Sun 8/166:30 am
MDW
- DEN
Nonstop2h 30m
Southwest
Deal found 7/15![Southwest logo]()
$235
This United Airlines deal was found by Cheapflights users on 7/14. 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.
Tue 8/48:45 pm
DEN
- STL
Nonstop2h 12m
United Airlines
Sat 8/221:36 pm
STL
- DEN
Nonstop2h 24m
United Airlines
Deal found 7/14![United Airlines logo]()
$267
This Delta deal was found by Cheapflights users on 7/14. 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.
Thu 11/56:10 am
DEN
- ORD
1 stop5h 51m
Delta
Sun 11/86:30 am
ORD
- DEN
1 stop4h 27m
Delta
Deal found 7/14![Delta logo]()
$255
This Southwest deal was found by Cheapflights users on 7/16. 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 Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 8/213:15 pm
DEN
- MDW
1 stop3h 30m
Southwest
Mon 8/244:25 pm
MDW
- DEN
Nonstop2h 35m
Southwest
Deal found 7/16![Southwest logo]()
$241
This Delta deal was found by Cheapflights users on 7/15. 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 Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 9/238:45 am
DEN
- ORD
1 stop5h 20m
Delta
Sun 9/275:10 pm
ORD
- DEN
1 stop5h 23m
Delta
Deal found 7/15![Delta logo]()
$255
This United Airlines deal was found by Cheapflights users on 7/12. 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 10/77:10 pm
DEN
- ORD
Nonstop2h 36m
United Airlines
Mon 10/1210:00 pm
ORD
- DEN
Nonstop2h 54m
United Airlines
Deal found 7/12![United Airlines logo]()
$285
Last-minute flights from Colorado to IllinoisDiscover last-minute flight deals from Colorado to Illinois. Data last updated July 17, 2026 and is based on user searches.
Discover last-minute flight deals from Colorado to Illinois. Data last updated July 17, 2026 and is based on user searches.
This Super.com deal was found by Cheapflights users on 7/15. 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 Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 8/45:05 pm
DEN
- ORD
Nonstop2h 47m
Frontier
Tue 8/119:57 pm
ORD
- DEN
Nonstop3h 00m
Frontier
Deal found 7/15![Frontier logo]()
$174
This Kiwi.com deal was found by Cheapflights users on 7/13. 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 8/45:05 pm
DEN
- ORD
Nonstop2h 47m
Frontier
Fri 8/79:57 pm
ORD
- DEN
Nonstop3h 00m
Frontier
Deal found 7/13![Frontier logo]()
$175
This Cheapflightsfares deal was found by Cheapflights users on 7/13. 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 Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 8/55:05 pm
DEN
- ORD
Nonstop2h 47m
Frontier
Mon 8/109:57 pm
ORD
- DEN
Nonstop3h 00m
Frontier
Deal found 7/13![Frontier logo]()
$182
This Frontier deal was found by Cheapflights users on 7/13. 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.
Fri 8/75:05 pm
DEN
- ORD
Nonstop2h 47m
Frontier
Wed 8/192:41 pm
ORD
- DEN
Nonstop3h 04m
Frontier
Deal found 7/13![Frontier logo]()
$176
This Trip.com deal was found by Cheapflights users on 7/16. 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 Trip.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 8/85:05 pm
DEN
- ORD
Nonstop2h 47m
Frontier
Mon 8/109:57 pm
ORD
- DEN
Nonstop3h 00m
Frontier
Deal found 7/16![Frontier logo]()
$177
This Kiwi.com deal was found by Cheapflights users on 7/16. 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 Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 8/118:52 pm
DEN
- ORD
2 stops46h 01m
Frontier
Tue 8/182:41 pm
ORD
- DEN
Nonstop3h 04m
Frontier
Deal found 7/16![Frontier logo]()
$179
This Frontier deal was found by Cheapflights users on 7/13. 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.
Wed 8/125:05 pm
DEN
- ORD
Nonstop2h 47m
Frontier
Mon 8/179:57 pm
ORD
- DEN
Nonstop3h 00m
Frontier
Deal found 7/13![Frontier logo]()
$181
This Cheapflightsfares deal was found by Cheapflights users on 7/12. 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.
Thu 8/134:27 pm
DEN
- PIA
Nonstop2h 10m
Allegiant Air
Sun 8/2310:07 am
PIA
- DEN
Nonstop2h 19m
Allegiant Air
Deal found 7/12![Allegiant Air logo]()
$154
This Kiwi.com deal was found by Cheapflights users on 7/14. 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.
Mon 8/174:10 pm
DEN
- STL
Nonstop2h 13m
Frontier
Fri 8/216:17 pm
STL
- DEN
1 stop16h 02m
Frontier
Deal found 7/14![Frontier logo]()
$182
This Cheapflightsfares deal was found by Cheapflights users on 7/15. 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 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 8/3010:07 am
PIA
- DEN
Nonstop2h 19m
Allegiant Air
Deal found 7/15![Allegiant Air logo]()
$146
This Super.com deal was found by Cheapflights users on 7/16. 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.
Wed 8/269:55 am
DEN
- ORD
Nonstop2h 41m
Frontier
Sun 8/302:41 pm
ORD
- DEN
Nonstop3h 04m
Frontier
Deal found 7/16![Frontier logo]()
$180
This Kiwi.com deal was found by Cheapflights users on 7/16. 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 Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 8/272:17 pm
DEN
- PIA
Nonstop2h 07m
Allegiant Air
Sun 9/610:07 am
PIA
- DEN
Nonstop2h 20m
Allegiant Air
Deal found 7/16![Allegiant Air logo]()
$176
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 July 17, 2026.
Search for one-way flight options from Colorado to Illinois. Find affordable one-way fares based on user searches. Data last updated July 17, 2026.
This Southwest deal was found by Cheapflights users on 7/15. 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.
Wed 9/238:35 am
DEN
- STL
Nonstop2h 05m
Southwest
Deal found 7/15![Southwest logo]()
$94
This Southwest deal was found by Cheapflights users on 7/13. 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 10/61:30 pm
DEN
- STL
1 stop3h 15m
Southwest
Deal found 7/13![Southwest logo]()
$99
This Cheapflightsfares deal was found by Cheapflights users on 7/14. 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.
Mon 8/104:10 pm
DEN
- STL
Nonstop2h 13m
Frontier
Deal found 7/14![Frontier logo]()
$100
This Kiwi.com deal was found by Cheapflights users on 7/12. 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 8/117:00 am
DEN
- ORD
1 stop16h 33m
Frontier
Deal found 7/12![Frontier logo]()
$102
This Cheapflightsfares deal was found by Cheapflights users on 7/13. 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 Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 8/411:59 pm
DEN
- ORD
1 stop7h 03m
Frontier
Deal found 7/13![Frontier logo]()
$103
This Southwest deal was found by Cheapflights users on 7/13. 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.
Thu 8/138:25 pm
DEN
- MDW
Nonstop2h 20m
Southwest
Deal found 7/13![Southwest logo]()
$103
This Trip.com deal was found by Cheapflights users on 7/15. 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.
Wed 9/2310:30 am
DEN
- STL
1 stop22h 10m
Frontier
Deal found 7/15![Frontier logo]()
$103
This Kiwi.com deal was found by Cheapflights users on 7/14. 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.
Sat 8/157:00 am
DEN
- ORD
1 stop16h 33m
Frontier
Deal found 7/14![Frontier logo]()
$104
This Super.com deal was found by Cheapflights users on 7/13. 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.
Tue 8/411:59 pm
DEN
- MDW
1 stop8h 52m
Frontier
Deal found 7/13![Frontier logo]()
$104
This Delta deal was found by Cheapflights users on 7/13. 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.
Sun 8/912:50 am
DEN
- STL
1 stop6h 18m
Delta
Deal found 7/13![Delta logo]()
$104
This Frontier deal was found by Cheapflights users on 7/13. 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.
Tue 8/2510:43 am
DEN
- ORD
1 stop8h 16m
Frontier
Deal found 7/13![Frontier logo]()
$105
This Frontier deal was found by Cheapflights users on 7/13. 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.
Tue 8/1111:59 pm
DEN
- MDW
1 stop8h 52m
Frontier
Deal found 7/13![Frontier logo]()
$105
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 July 17, 2026.
Most accurate provider | FlightHub 3 stars |
|---|---|
Most trusted provider | FlightHub 3 stars |
Round-trip from | $136 (Mytrip) |
One-way from | $94 (Southwest) |
Popular in | June |
Cheapest in | January |
Average price | $284 |
Good round-trip deal | $261 or less |
Good one-way deal | $152 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 July 17, 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
DenverSt. Louis
DEN - STL
DENSTL
Denver Intl
Thu 8/20
5:35 pm-8:46 pm
Nonstop2h 11m
Lambert-St Louis
Tue 8/25
1:36 pm-3:00 pm
Nonstop2h 24m
$187
DenverSt. Louis
DEN - STL
DENSTL
Denver Intl
Sat 8/15
9:35 am-12:40 pm
Nonstop2h 05m
Lambert-St Louis
Sat 8/22
8:30 am-2:31 pm
1 stop7h 01m
$197
DenverSt. Louis
DEN - STL
DENSTL
Denver Intl
Sat 8/29
11:15 am-3:30 pm
1 stop3h 15m
Lambert-St Louis
Sat 9/5
2:25 pm-6:40 pm
1 stop5h 15m
$202
DenverChicago
DEN - MDW
DENMDW
Denver Intl
Tue 10/6
7:00 am-10:20 am
Nonstop2h 20m
Chicago Midway
Thu 10/8
6:05 am-7:45 am
Nonstop2h 40m
$205
DenverChicago
DEN - ORD
DENORD
Denver Intl
Thu 8/6
9:05 pm-12:44 am
Nonstop2h 39m
Chicago O'Hare Intl
Mon 8/10
6:00 am-7:42 am
Nonstop2h 42m
$205
DenverChicago
DEN - ORD
DENORD
Denver Intl
Tue 8/11
8:29 pm-11:59 pm
Nonstop2h 30m
Chicago O'Hare Intl
Thu 8/13
10:00 pm-11:53 pm
Nonstop2h 53m
$205
DenverChicago
DEN - ORD
DENORD
Denver Intl
Thu 8/27
8:29 pm-11:59 pm
Nonstop2h 30m
Chicago O'Hare Intl
Sat 8/29
7:50 pm-9:44 pm
Nonstop2h 54m
$205
DenverSt. Louis
DEN - STL
DENSTL
Denver Intl
Wed 10/7
10:45 am-5:34 pm
1 stop5h 49m
Lambert-St Louis
Tue 10/13
10:15 am-5:08 pm
1 stop7h 53m
$207
DenverSt. Louis
DEN - STL
DENSTL
Denver Intl
Wed 9/2
6:00 am-2:33 pm
1 stop7h 33m
Lambert-St Louis
Wed 9/9
5:46 pm-10:55 pm
1 stop6h 09m
$207
DenverChicago
DEN - MDW
DENMDW
Denver Intl
Sat 8/22
11:10 am-5:10 pm
1 stop5h 00m
Chicago Midway
Tue 8/25
12:00 pm-1:30 pm
Nonstop2h 30m
$211
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-ORD
DEN-STL
DEN-MDW
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-PIA
DEN-ORD
DEN-STL
DEN-MDW
What is the cheapest month to book a flight from Colorado to Illinois?
Currently, September is the cheapest month in which you can book a flight from Colorado to Illinois (average of $230). Flying from Colorado to Illinois in December is currently the most expensive (average of $368). 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 July 17, 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.
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 July 17, 2026.
The most flights from USCO to USIL are scheduled on a Thursday (74 on average). You will have fewer flight options on Saturday, which is when the least amount of flights are scheduled (26 on average).
How much does it cost to fly round-trip from Colorado to Illinois?
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 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 July 11, 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.
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 July 17, 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.
Food
7.0
Overall
8.0
Boarding
8.1
Crew
8.6
Entertainment
7.5
Comfort
8.0
Reviews
1 / 20
6.0
GoodReza,Jun 2026
TPA - MDW
Food
7.0
Overall
8.0
Boarding
8.1
Crew
8.6
Entertainment
7.5
Comfort
8.0
Reviews
1 / 20
6.0
GoodReza,Jun 2026
TPA - MDW
Food
7.0
Overall
8.0
Boarding
8.1
Crew
8.6
Entertainment
7.5
Comfort
8.0
Reviews
1 / 20
6.0
GoodReza,Jun 2026
TPA - MDW
Food
7.0
Overall
8.0
Boarding
8.1
Crew
8.6
Entertainment
7.5
Comfort
8.0
Reviews
1 / 20
6.0
GoodReza,Jun 2026
TPA - MDW
Food
7.0
Overall
8.0
Boarding
8.1
Crew
8.6
Entertainment
7.5
Comfort
8.0
Reviews
1 / 20
6.0
GoodReza,Jun 2026
TPA - MDW
Food
7.0
Overall
8.0
Boarding
8.1
Crew
8.6
Entertainment
7.5
Comfort
8.0
Reviews
1 / 20
6.0
GoodReza,Jun 2026
TPA - MDW
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
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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 July 17, 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 July 17, 2026.
| Airline | Cheapest | Average | Flexibility | On-time |
|---|---|---|---|---|
| Cheapest$76 | Average$193 | FlexibilityNo cancel fee | On-time62% | |
| Cheapest$84 | Average$168 | FlexibilityNo cancel fee | On-time88% | |
| Cheapest$126 | Average$281 | FlexibilityNo cancel fee | On-time62% | |
| Cheapest$157 | Average$337 | FlexibilityNo cancel fee | On-time63% | |
| Cheapest$166 | Average$432 | FlexibilityNo cancel fee | On-time71% | |
| Cheapest$177 | Average$445 | FlexibilityNo cancel fee | On-time69% |