$92+ 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 8/11. Fares are subject to change and may not be available on all flights or dates of travel.
DEN — ORD
Jul 16 — Jul 231
Round-trip
1 adult, Economy
We work with more than 300 partners to bring you better travel deals
Find cheap flights from Colorado to Illinois with Cheapflights
1. Tell us where you want to go
Enter your travel information like dates, passengers, trip type (one-way or round trip), and preferred cabin class then click “Find deals”2. Select your favorite providers
We find the providers serving your travel needs. Choose up to four travel providers to compare side-by-side for flights, hotels, or car rentals.3. Compare prices and book
Review each provider’s pricing and select the best option for you! Book through your favorite provider’s website for a seamless experience.Cheap flight deals from Colorado to Illinois
Cheapest
Best
Last-minute
One-way
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 June 16, 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 June 16, 2026.
This Cheapflightsfares deal was found by Cheapflights users on 6/11. 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.
Thu 10/2910:20 am
DEN
- PIA
Nonstop1h 59m
Allegiant Air
Sun 11/15:24 pm
PIA
- DEN
Nonstop2h 20m
Allegiant Air
Deal found 6/11![Allegiant Air logo]()
$104
This Frontier deal was found by Cheapflights users on 6/16. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 8/154:10 pm
DEN
- STL
Nonstop2h 13m
Frontier
Mon 8/178:08 pm
STL
- DEN
Nonstop2h 36m
Frontier
Deal found 6/16![Frontier logo]()
$166
This Kiwi.com deal was found by Cheapflights users on 6/12. 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 8/184:12 pm
DEN
- STL
Nonstop2h 11m
Frontier
Sat 8/228:08 pm
STL
- DEN
Nonstop2h 36m
Frontier
Deal found 6/12![Frontier logo]()
$167
This Frontier deal was found by Cheapflights users on 6/11. 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 7/84:10 pm
DEN
- STL
Nonstop2h 13m
Frontier
Sat 7/118:08 pm
STL
- DEN
Nonstop2h 36m
Frontier
Deal found 6/11![Frontier logo]()
$168
This Cheapflightsfares deal was found by Cheapflights users on 6/12. 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 7/154:10 pm
DEN
- STL
Nonstop2h 13m
Frontier
Sat 7/188:08 pm
STL
- DEN
Nonstop2h 36m
Frontier
Deal found 6/12![Frontier logo]()
$169
This Cheapflightsfares deal was found by Cheapflights users on 6/13. 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 7/14:12 pm
DEN
- STL
Nonstop2h 11m
Frontier
Tue 7/78:08 pm
STL
- DEN
Nonstop2h 36m
Frontier
Deal found 6/13![Frontier logo]()
$170
This Frontier deal was found by Cheapflights users on 6/14. 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 Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 7/244:10 pm
DEN
- STL
Nonstop2h 13m
Frontier
Wed 7/298:08 pm
STL
- DEN
Nonstop2h 36m
Frontier
Deal found 6/14![Frontier logo]()
$172
This Kiwi.com deal was found by Cheapflights users on 6/14. 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 7/14:12 pm
DEN
- STL
Nonstop2h 11m
Frontier
Sat 7/47:38 pm
STL
- DEN
Nonstop2h 26m
Frontier
Deal found 6/14![Frontier logo]()
$176
This Kiwi.com deal was found by Cheapflights users on 6/15. 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 Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 7/144:10 pm
DEN
- STL
Nonstop2h 13m
Frontier
Mon 7/277:10 pm
STL
- DEN
1 stop9h 38m
Frontier
Deal found 6/15![Frontier logo]()
$177
This Kiwi.com deal was found by Cheapflights users on 6/14. 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.
Thu 8/134:27 pm
DEN
- PIA
Nonstop2h 10m
Allegiant Air
Sun 8/165:23 pm
PIA
- DEN
Nonstop2h 25m
Allegiant Air
Deal found 6/14![Allegiant Air logo]()
$178
This Frontier deal was found by Cheapflights users on 6/15. 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 Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 9/254:12 pm
DEN
- STL
Nonstop2h 03m
Frontier
Sun 9/278:10 pm
STL
- DEN
Nonstop2h 39m
Frontier
Deal found 6/15![Frontier logo]()
$178
This Cheapflightsfares deal was found by Cheapflights users on 6/14. 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.
Thu 9/104:12 pm
DEN
- STL
Nonstop2h 03m
Frontier
Sun 9/138:10 pm
STL
- DEN
Nonstop2h 39m
Frontier
Deal found 6/14![Frontier logo]()
$179
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 June 16, 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 June 16, 2026.
This United Airlines deal was found by Cheapflights users on 6/11. 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.
Wed 7/299:05 pm
DEN
- ORD
Nonstop2h 39m
United Airlines
Wed 8/125:55 am
ORD
- DEN
Nonstop2h 39m
United Airlines
Deal found 6/11![United Airlines logo]()
$188
This Delta deal was found by Cheapflights users on 6/11. 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.
Tue 9/228:55 am
DEN
- ORD
1 stop7h 28m
Delta
Thu 10/15:10 pm
ORD
- DEN
1 stop5h 14m
Delta
Deal found 6/11![Delta logo]()
$204
This Southwest deal was found by Cheapflights users on 6/11. 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.
Thu 7/307:05 pm
DEN
- MDW
1 stop5h 00m
Southwest
Wed 8/58:55 am
MDW
- DEN
1 stop5h 00m
Southwest
Deal found 6/11![Southwest logo]()
$228
This Delta deal was found by Cheapflights users on 6/11. 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 10/216:45 am
DEN
- ORD
1 stop4h 52m
Delta
Sat 10/2411:30 am
ORD
- DEN
1 stop7h 00m
Delta
Deal found 6/11![Delta logo]()
$204
This American Airlines deal was found by Cheapflights users on 6/12. 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 7/310:31 am
ASE
- ORD
1 stop6h 45m
American Airlines
Mon 7/67:49 pm
ORD
- ASE
Nonstop3h 07m
American Airlines
Deal found 6/12![American Airlines logo]()
$429
This Delta deal was found by Cheapflights users on 6/11. 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 9/246:05 am
DEN
- ORD
1 stop5h 59m
Delta
Thu 10/15:10 pm
ORD
- DEN
1 stop5h 14m
Delta
Deal found 6/11![Delta logo]()
$211
This Southwest deal was found by Cheapflights users on 6/14. 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.
Wed 8/126:30 am
DEN
- MDW
Nonstop2h 20m
Southwest
Sun 8/167:55 am
MDW
- DEN
Nonstop2h 45m
Southwest
Deal found 6/14![Southwest logo]()
$235
This Delta deal was found by Cheapflights users on 6/11. 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.
Mon 9/216:05 am
DEN
- ORD
1 stop5h 59m
Delta
Mon 9/289:00 am
ORD
- DEN
1 stop5h 51m
Delta
Deal found 6/11![Delta logo]()
$211
This Southwest deal was found by Cheapflights users on 6/16. 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 9/116:30 pm
DEN
- MDW
Nonstop2h 30m
Southwest
Tue 9/1511:10 am
MDW
- DEN
1 stop4h 50m
Southwest
Deal found 6/16![Southwest logo]()
$241
This United Airlines deal was found by Cheapflights users on 6/12. 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 9/239:35 am
DEN
- STL
Nonstop2h 05m
United Airlines
Wed 9/301:36 pm
STL
- DEN
Nonstop2h 24m
United Airlines
Deal found 6/12![United Airlines logo]()
$285
This Southwest deal was found by Cheapflights users on 6/11. 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.
Sun 7/198:55 pm
DEN
- MDW
Nonstop2h 25m
Southwest
Tue 8/116:40 am
MDW
- DEN
Nonstop2h 30m
Southwest
Deal found 6/11![Southwest logo]()
$242
This United Airlines deal was found by Cheapflights users on 6/16. 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.
Tue 8/111:27 pm
DEN
- STL
Nonstop2h 07m
United Airlines
Tue 8/181:36 pm
STL
- DEN
Nonstop2h 24m
United Airlines
Deal found 6/16![United Airlines logo]()
$285
This Delta deal was found by Cheapflights users on 6/15. 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.
Tue 9/86:05 am
DEN
- ORD
1 stop5h 59m
Delta
Sat 9/128:55 am
ORD
- DEN
1 stop6h 03m
Delta
Deal found 6/15![Delta logo]()
$236
This Southwest deal was found by Cheapflights users on 6/16. 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.
Thu 7/237:05 pm
DEN
- MDW
1 stop5h 00m
Southwest
Tue 7/285:30 am
MDW
- DEN
Nonstop2h 35m
Southwest
Deal found 6/16![Southwest logo]()
$245
This Delta deal was found by Cheapflights users on 6/13. 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.
Wed 10/74:00 pm
DEN
- ORD
1 stop4h 34m
Delta
Thu 10/85:20 pm
ORD
- DEN
1 stop6h 39m
Delta
Deal found 6/13![Delta logo]()
$236
This United Airlines deal was found by Cheapflights users on 6/13. 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 7/45:44 am
COS
- ORD
Nonstop3h 01m
United Airlines
Tue 7/75:00 am
ORD
- COS
1 stop4h 41m
United Airlines
Deal found 6/13![United Airlines logo]()
$289
This Southwest deal was found by Cheapflights users on 6/12. 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 8/811:15 am
DEN
- MDW
1 stop4h 40m
Southwest
Wed 8/128:50 pm
MDW
- DEN
Nonstop2h 35m
Southwest
Deal found 6/12![Southwest logo]()
$252
This Delta deal was found by Cheapflights users on 6/13. 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 8/202:22 pm
DEN
- ORD
1 stop5h 08m
Delta
Tue 8/256:45 pm
ORD
- DEN
1 stop5h 49m
Delta
Deal found 6/13![Delta logo]()
$236
This United Airlines deal was found by Cheapflights users on 6/14. 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.
Wed 8/55:38 pm
DEN
- MLI
Nonstop2h 16m
United Airlines
Sun 8/96:30 pm
MLI
- DEN
1 stop6h 18m
United Airlines
Deal found 6/14![United Airlines logo]()
$291
This Delta deal was found by Cheapflights users on 6/14. 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.
Tue 8/116:05 am
DEN
- MDW
1 stop5h 34m
Delta
Mon 8/177:25 pm
MDW
- DEN
1 stop5h 09m
Delta
Deal found 6/14![Delta logo]()
$236
This Southwest deal was found by Cheapflights users on 6/11. 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.
Wed 7/297:40 am
DEN
- MDW
Nonstop2h 25m
Southwest
Sat 8/15:25 am
MDW
- DEN
Nonstop2h 35m
Southwest
Deal found 6/11![Southwest logo]()
$265
This United Airlines deal was found by Cheapflights users on 6/14. 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.
Wed 8/56:00 am
DEN
- PIA
1 stop5h 38m
United Airlines
Sun 8/96:12 pm
PIA
- DEN
1 stop6h 36m
United Airlines
Deal found 6/14![United Airlines logo]()
$300
This Southwest deal was found by Cheapflights users on 6/16. 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.
Wed 7/158:10 am
DEN
- MDW
1 stop5h 25m
Southwest
Sat 7/185:25 am
MDW
- DEN
Nonstop2h 35m
Southwest
Deal found 6/16![Southwest logo]()
$265
This Delta deal was found by Cheapflights users on 6/11. 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.
Sun 9/206:00 am
DEN
- ORD
1 stop4h 49m
Delta
Wed 9/305:10 pm
ORD
- DEN
1 stop5h 14m
Delta
Deal found 6/11![Delta logo]()
$241
This United Airlines deal was found by Cheapflights users on 6/15. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 8/2510:27 am
COS
- STL
1 stop5h 07m
United Airlines
Wed 8/265:10 am
STL
- COS
1 stop6h 34m
United Airlines
Deal found 6/15![United Airlines logo]()
$305
This Delta deal was found by Cheapflights users on 6/13. 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.
Sat 8/86:05 am
DEN
- ORD
1 stop6h 45m
Delta
Mon 8/105:57 pm
ORD
- DEN
1 stop6h 37m
Delta
Deal found 6/13![Delta logo]()
$247
This Southwest deal was found by Cheapflights users on 6/12. 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.
Thu 8/138:25 pm
DEN
- MDW
Nonstop2h 20m
Southwest
Sun 8/236:30 am
MDW
- DEN
Nonstop2h 30m
Southwest
Deal found 6/12![Southwest logo]()
$275
This United Airlines deal was found by Cheapflights users on 6/15. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 7/106:32 pm
COS
- STL
1 stop4h 25m
United Airlines
Tue 7/145:10 am
STL
- COS
1 stop4h 31m
United Airlines
Deal found 6/15![United Airlines logo]()
$306
This Delta deal was found by Cheapflights users on 6/12. 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 11/1110:30 am
DEN
- ORD
1 stop7h 10m
Delta
Mon 11/167:05 am
ORD
- DEN
1 stop7h 58m
Delta
Deal found 6/12![Delta logo]()
$247
This United Airlines deal was found by Cheapflights users on 6/15. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 9/191:27 pm
DEN
- STL
Nonstop2h 07m
United Airlines
Thu 9/241:36 pm
STL
- DEN
Nonstop2h 24m
United Airlines
Deal found 6/15![United Airlines logo]()
$313
Last-minute flights from Colorado to IllinoisDiscover last-minute flight deals from Colorado to Illinois. Data last updated June 16, 2026 and is based on user searches.
Discover last-minute flight deals from Colorado to Illinois. Data last updated June 16, 2026 and is based on user searches.
This Cheapflightsfares deal was found by Cheapflights users on 6/13. 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 7/14:12 pm
DEN
- STL
Nonstop2h 11m
Frontier
Tue 7/78:08 pm
STL
- DEN
Nonstop2h 36m
Frontier
Deal found 6/13![Frontier logo]()
$170
This Kiwi.com deal was found by Cheapflights users on 6/14. 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 7/14:12 pm
DEN
- STL
Nonstop2h 11m
Frontier
Sat 7/47:38 pm
STL
- DEN
Nonstop2h 26m
Frontier
Deal found 6/14![Frontier logo]()
$176
This Frontier deal was found by Cheapflights users on 6/11. 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 7/84:10 pm
DEN
- STL
Nonstop2h 13m
Frontier
Sat 7/118:08 pm
STL
- DEN
Nonstop2h 36m
Frontier
Deal found 6/11![Frontier logo]()
$168
This Cheapflightsfares deal was found by Cheapflights users on 6/13. 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 7/84:10 pm
DEN
- STL
Nonstop2h 13m
Frontier
Tue 7/148:08 pm
STL
- DEN
Nonstop2h 36m
Frontier
Deal found 6/13![Frontier logo]()
$180
This Super.com deal was found by Cheapflights users on 6/11. 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 7/85:05 pm
DEN
- ORD
Nonstop2h 47m
Frontier
Tue 7/149:57 pm
ORD
- DEN
Nonstop3h 00m
Frontier
Deal found 6/11![Frontier logo]()
$181
This Frontier deal was found by Cheapflights users on 6/11. 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.
Thu 7/94:10 pm
DEN
- STL
Nonstop2h 13m
Frontier
Sat 7/118:08 pm
STL
- DEN
Nonstop2h 36m
Frontier
Deal found 6/11![Frontier logo]()
$178
This Kiwi.com deal was found by Cheapflights users on 6/15. 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 Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 7/144:25 pm
DEN
- STL
1 stop24h 40m
Frontier
Tue 7/218:08 pm
STL
- DEN
Nonstop2h 36m
Frontier
Deal found 6/15![Frontier logo]()
$177
This Kiwi.com deal was found by Cheapflights users on 6/15. 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 Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 7/144:10 pm
DEN
- STL
Nonstop2h 13m
Frontier
Fri 7/314:57 pm
STL
- DEN
1 stop17h 06m
Frontier
Deal found 6/15![Frontier logo]()
$181
This Cheapflightsfares deal was found by Cheapflights users on 6/12. 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 7/154:10 pm
DEN
- STL
Nonstop2h 13m
Frontier
Sat 7/188:08 pm
STL
- DEN
Nonstop2h 36m
Frontier
Deal found 6/12![Frontier logo]()
$169
This Trip.com deal was found by Cheapflights users on 6/12. 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 Trip.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 7/165:05 pm
DEN
- ORD
Nonstop2h 47m
Frontier
Fri 7/319:57 pm
ORD
- DEN
Nonstop3h 00m
Frontier
Deal found 6/12![Frontier logo]()
$182
This Cheapflightsfares deal was found by Cheapflights users on 6/15. 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.
Fri 7/244:10 pm
DEN
- STL
Nonstop2h 13m
Frontier
Tue 7/288:08 pm
STL
- DEN
Nonstop2h 36m
Frontier
Deal found 6/15![Frontier logo]()
$166
This Frontier deal was found by Cheapflights users on 6/14. 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 Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 7/244:10 pm
DEN
- STL
Nonstop2h 13m
Frontier
Wed 7/298:08 pm
STL
- DEN
Nonstop2h 36m
Frontier
Deal found 6/14![Frontier logo]()
$172
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 June 16, 2026.
Search for one-way flight options from Colorado to Illinois. Find affordable one-way fares based on user searches. Data last updated June 16, 2026.
This Kiwi.com deal was found by Cheapflights users on 6/12. 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 8/1110:09 am
DEN
- ORD
1 stop9h 06m
Frontier
Deal found 6/12![Frontier logo]()
$92
This Kiwi.com deal was found by Cheapflights users on 6/11. 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 8/1210:00 am
DEN
- ORD
1 stop18h 37m
Frontier
Deal found 6/11![Frontier logo]()
$93
This Kiwi.com deal was found by Cheapflights users on 6/12. 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.
Wed 9/95:17 pm
DEN
- ORD
1 stop30h 07m
Frontier
Deal found 6/12![Frontier logo]()
$94
This Kiwi.com deal was found by Cheapflights users on 6/12. 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.
Wed 9/95:17 pm
DEN
- MDW
1 stop17h 50m
Frontier
Deal found 6/12![Frontier logo]()
$94
This United Airlines deal was found by Cheapflights users on 6/11. 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.
Mon 8/109:05 pm
DEN
- ORD
Nonstop2h 39m
United Airlines
Deal found 6/11![United Airlines logo]()
$96
This Delta deal was found by Cheapflights users on 6/12. 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 8/196:05 am
DEN
- ORD
1 stop6h 03m
Delta
Deal found 6/12![Delta logo]()
$99
This Delta deal was found by Cheapflights users on 6/11. 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.
Tue 8/46:05 am
DEN
- MDW
1 stop5h 34m
Delta
Deal found 6/11![Delta logo]()
$99
This Kiwi.com deal was found by Cheapflights users on 6/11. 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.
Mon 8/105:23 pm
DEN
- MDW
1 stop22h 28m
Frontier
Deal found 6/11![Frontier logo]()
$101
This Cheapflightsfares deal was found by Cheapflights users on 6/14. 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.
Sun 9/132:26 pm
DEN
- PIA
Nonstop2h 03m
Allegiant Air
Deal found 6/14![Allegiant Air logo]()
$101
This Kiwi.com deal was found by Cheapflights users on 6/13. 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.
Mon 8/105:23 pm
DEN
- ORD
1 stop25h 52m
Frontier
Deal found 6/13![Frontier logo]()
$102
This Cheapflightsfares deal was found by Cheapflights users on 6/16. 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 Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 8/1911:42 pm
DEN
- ORD
1 stop7h 21m
Frontier
Deal found 6/16![Frontier logo]()
$103
This Southwest deal was found by Cheapflights users on 6/16. 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.
Tue 7/146:15 am
DEN
- MDW
Nonstop2h 25m
Southwest
Deal found 6/16![Southwest logo]()
$103
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 June 16, 2026.
Most accurate provider | FlightHub 3 stars |
|---|---|
Most trusted provider | FlightHub 3 stars |
Round-trip from | $166 (Frontier) |
One-way from | $92 (Kiwi.com) |
Popular in | March |
Cheapest in | January |
Average price | $289 |
Good round-trip deal | $267 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 June 16, 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 7/29
9:05 pm-12:44 am
Nonstop2h 39m
Chicago O'Hare Intl
Wed 8/12
5:55 am-7:34 am
Nonstop2h 39m
$188
DenverChicago
DEN - ORD
DENORD
Denver Intl
Tue 9/22
8:55 am-5:23 pm
1 stop7h 28m
Chicago O'Hare Intl
Thu 10/1
5:10 pm-9:24 pm
1 stop5h 14m
$204
DenverChicago
DEN - ORD
DENORD
Denver Intl
Wed 10/21
6:45 am-12:37 pm
1 stop4h 52m
Chicago O'Hare Intl
Sat 10/24
11:30 am-5:30 pm
1 stop7h 00m
$204
DenverChicago
DEN - ORD
DENORD
Denver Intl
Thu 9/24
6:05 am-1:04 pm
1 stop5h 59m
Chicago O'Hare Intl
Thu 10/1
5:10 pm-9:24 pm
1 stop5h 14m
$211
DenverChicago
DEN - ORD
DENORD
Denver Intl
Mon 9/21
6:05 am-1:04 pm
1 stop5h 59m
Chicago O'Hare Intl
Mon 9/28
9:00 am-1:51 pm
1 stop5h 51m
$211
DenverChicago
DEN - MDW
DENMDW
Denver Intl
Thu 7/30
7:05 pm-1:05 am
1 stop5h 00m
Chicago Midway
Wed 8/5
8:55 am-12:55 pm
1 stop5h 00m
$228
DenverChicago
DEN - MDW
DENMDW
Denver Intl
Wed 8/12
6:30 am-9:50 am
Nonstop2h 20m
Chicago Midway
Sun 8/16
7:55 am-9:40 am
Nonstop2h 45m
$235
DenverChicago
DEN - ORD
DENORD
Denver Intl
Tue 9/8
6:05 am-1:04 pm
1 stop5h 59m
Chicago O'Hare Intl
Sat 9/12
8:55 am-1:58 pm
1 stop6h 03m
$236
DenverChicago
DEN - ORD
DENORD
Denver Intl
Wed 10/7
4:00 pm-9:34 pm
1 stop4h 34m
Chicago O'Hare Intl
Thu 10/8
5:20 pm-10:59 pm
1 stop6h 39m
$236
DenverChicago
DEN - ORD
DENORD
Denver Intl
Thu 8/20
2:22 pm-8:30 pm
1 stop5h 08m
Chicago O'Hare Intl
Tue 8/25
6:45 pm-11:34 pm
1 stop5h 49m
$236
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
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 $225). Flying from Colorado to Illinois in December is currently the most expensive (average of $376). 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 June 16, 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 June 16, 2026.
The most flights from USCO to USIL are scheduled on a Tuesday (72 on average). You will have fewer flight options on Saturday, which is when the least amount of flights are scheduled (41 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 June 13, 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 June 16, 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.
Boarding
8.1
Crew
8.6
Overall
7.9
Entertainment
7.5
Food
7.0
Comfort
8.0
Reviews
1 / 20
8.0
ExcellentLa Tracimeldamarcos,Jun 2026
LAX - SLC
Boarding
8.1
Crew
8.6
Overall
7.9
Entertainment
7.5
Food
7.0
Comfort
8.0
Reviews
1 / 20
8.0
ExcellentLa Tracimeldamarcos,Jun 2026
LAX - SLC
Boarding
8.1
Crew
8.6
Overall
7.9
Entertainment
7.5
Food
7.0
Comfort
8.0
Reviews
1 / 20
8.0
ExcellentLa Tracimeldamarcos,Jun 2026
LAX - SLC
Boarding
8.1
Crew
8.6
Overall
7.9
Entertainment
7.5
Food
7.0
Comfort
8.0
Reviews
1 / 20
8.0
ExcellentLa Tracimeldamarcos,Jun 2026
LAX - SLC
Boarding
8.1
Crew
8.6
Overall
7.9
Entertainment
7.5
Food
7.0
Comfort
8.0
Reviews
1 / 20
8.0
ExcellentLa Tracimeldamarcos,Jun 2026
LAX - SLC
Boarding
8.1
Crew
8.6
Overall
7.9
Entertainment
7.5
Food
7.0
Comfort
8.0
Reviews
1 / 20
8.0
ExcellentLa Tracimeldamarcos,Jun 2026
LAX - SLC
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.
Alternative routes
Complete your trip
Flights by cabin class
Other flight options
Popular flights
Return Flight Options
Top destinations
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 June 16, 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 June 16, 2026.
| Airline | Cheapest | Average | Flexibility | On-time |
|---|---|---|---|---|
| Cheapest$75 | Average$188 | FlexibilityNo cancel fee | On-time62% | |
| Cheapest$84 | Average$160 | FlexibilityNo cancel fee | On-time88% | |
| Cheapest$126 | Average$233 | FlexibilityNo cancel fee | On-time62% | |
| Cheapest$157 | Average$321 | FlexibilityNo cancel fee | On-time63% | |
| Cheapest$168 | Average$430 | FlexibilityNo cancel fee | On-time71% | |
| Cheapest$176 | Average$434 | FlexibilityNo cancel fee | On-time69% |