$24+ 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 12/6. Fares are subject to change and may not be available on all flights or dates of travel.
DEN — ORD
Dec 19 — Dec 261
1 adult, Economy
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Cheapest flights from Colorado to IllinoisExplore the most affordable flight options available from Colorado to Illinois. Find the lowest fares from popular airlines and budget airlines, with prices last updated on November 19, 2025.
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 November 19, 2025.
This Cheapflightsfares deal was found by Cheapflights users on 11/18. Clicking the “Pick Dates” 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 12/55:24 pmDEN - PIA
Nonstop1h 57mAllegiant Air
Mon 12/83:08 pmPIA - DEN
Nonstop2h 26mAllegiant Air
Deal found 11/18![Allegiant Air logo]()
$102
This Super.com deal was found by Cheapflights users on 11/16. 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.
Fri 12/127:05 amDEN - STL
Nonstop2h 09mFrontier
Mon 12/1512:07 pmSTL - DEN
1 stop7h 01mFrontier
Deal found 11/16![Frontier logo]()
$103
This Expedia deal was found by Cheapflights users on 11/17. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Expedia is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 12/1012:59 amDEN - STL
1 stop9h 08mFrontier
Mon 12/157:43 pmSTL - DEN
Nonstop2h 32mFrontier
Deal found 11/17![Frontier logo]()
$104
This Super.com deal was found by Cheapflights users on 11/18. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 12/47:00 amDEN - MDW
1 stop6h 04mFrontier
Mon 12/812:18 pmMDW - DEN
Nonstop2h 44mFrontier
Deal found 11/18![Frontier logo]()
$108
This Kiwi.com deal was found by Cheapflights users on 11/17. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 12/58:45 pmDEN - ORD
Nonstop2h 27mFrontier
Thu 12/115:15 amORD - DEN
1 stop15h 30mFrontier
Deal found 11/17![Frontier logo]()
$109
This CheapOair deal was found by Cheapflights users on 11/18. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure CheapOair is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 12/311:59 pmDEN - MDW
1 stop20h 59mFrontier
Mon 12/812:18 pmMDW - DEN
Nonstop2h 44mFrontier
Deal found 11/18![Frontier logo]()
$109
This Super.com deal was found by Cheapflights users on 11/17. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 12/611:59 pmDEN - STL
1 stop8h 00mFrontier
Tue 12/93:30 pmSTL - DEN
1 stop8h 34mFrontier
Deal found 11/17![Frontier logo]()
$109
This Frontier deal was found by Cheapflights users on 11/18. Clicking the “Pick Dates” 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 12/46:00 amDEN - ORD
1 stop13h 43mFrontier
Mon 12/89:27 pmORD - DEN
1 stop12h 28mFrontier
Deal found 11/18![Frontier logo]()
$110
This Kiwi.com deal was found by Cheapflights users on 11/18. Clicking the “Pick Dates” 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 12/57:45 amDEN - MDW
Nonstop2h 23mFrontier
Sun 12/78:05 amMDW - DEN
1 stop16h 54mFrontier
Deal found 11/18![Frontier logo]()
$111
This Kiwi.com deal was found by Cheapflights users on 11/18. Clicking the “Pick Dates” 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 12/268:45 pmDEN - ORD
Nonstop2h 27mFrontier
Mon 1/52:57 pmORD - DEN
1 stop7h 15mFrontier
Deal found 11/18![Frontier logo]()
$112
This CheapOair deal was found by Cheapflights users on 11/17. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure CheapOair is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sun 12/286:27 pmDEN - MDW
Nonstop2h 23mFrontier
Sun 1/410:50 pmMDW - DEN
Nonstop2h 55mFrontier
Deal found 11/17![Frontier logo]()
$112
This Booking.com deal was found by Cheapflights users on 11/17. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Booking.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 12/55:24 pmDEN - PIA
Nonstop1h 57mAllegiant Air
Fri 12/123:08 pmPIA - DEN
Nonstop2h 26mAllegiant Air
Deal found 11/17![Allegiant Air logo]()
$112
Cheap flight deals from Colorado to Illinois
Keep the following information in mind while searching for Colorado to Illinois flight deals. Data was last updated November 19, 2025.
Most accurate provider | CheapOair 3 stars |
|---|---|
Most trusted provider | CheapOair 3 stars |
Round-trip from | $102 (Cheapflightsfares) |
One-way from | $24 (Kiwi.com) |
Popular in | October |
Cheapest in | February |
Average price | $225 |
Good round-trip deal | $147 or less |
Good one-way deal | $96 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 November 19, 2025.
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
DenverPeoria
DEN - PIA
DENPIA
Denver Intl
Fri 12/5
5:24 pm-8:21 pm
Nonstop1h 57m
Greater Peoria
Mon 12/8
3:08 pm-4:34 pm
Nonstop2h 26m
$102
DenverPeoria
DEN - PIA
DENPIA
Denver Intl
Mon 12/29
5:54 pm-8:51 pm
Nonstop1h 57m
Greater Peoria
Mon 1/5
3:38 pm-5:04 pm
Nonstop2h 26m
$138
DenverChicago
DEN - ORD
DENORD
Denver Intl
Fri 1/9
5:42 pm-9:15 pm
Nonstop2h 33m
Chicago O'Hare Intl
Sun 1/11
6:15 pm-8:13 pm
Nonstop2h 58m
$155
DenverChicago
DEN - MDW
DENMDW
Denver Intl
Fri 1/30
6:25 pm-9:50 pm
Nonstop2h 25m
Chicago Midway
Mon 2/2
7:55 pm-9:40 pm
Nonstop2h 45m
$155
DenverChicago
DEN - ORD
DENORD
Denver Intl
Wed 2/18
7:24 pm-10:53 pm
Nonstop2h 29m
Chicago O'Hare Intl
Sun 2/22
9:05 pm-10:56 pm
Nonstop2h 51m
$155
DenverChicago
DEN - MDW
DENMDW
Denver Intl
Thu 1/8
6:25 pm-9:50 pm
Nonstop2h 25m
Chicago Midway
Sun 1/11
8:50 pm-10:35 pm
Nonstop2h 45m
$155
DenverChicago
DEN - MDW
DENMDW
Denver Intl
Wed 1/7
9:45 am-1:10 pm
Nonstop2h 25m
Chicago Midway
Sun 1/11
8:50 pm-10:35 pm
Nonstop2h 45m
$155
DenverChicago
DEN - MDW
DENMDW
Denver Intl
Wed 1/7
9:45 am-1:10 pm
Nonstop2h 25m
Chicago Midway
Sat 1/10
7:40 pm-9:25 pm
Nonstop2h 45m
$155
DenverChicago
DEN - MDW
DENMDW
Denver Intl
Tue 12/9
4:45 pm-8:05 pm
Nonstop2h 20m
Chicago Midway
Wed 12/10
9:40 am-11:20 am
Nonstop2h 40m
$179
DenverChicago
DEN - MDW
DENMDW
Denver Intl
Wed 12/10
8:00 am-11:25 am
Nonstop2h 25m
Chicago Midway
Wed 12/10
2:35 pm-4:15 pm
Nonstop2h 40m
$179
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.
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
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 $110). 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 November 19, 2025.
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 37% 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 November 2, 2025.
Travelers seeking maximum savings on their Colorado to Illinois flight should consider departing on Tuesday mornings 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 November 19, 2025.
The most flights from USCO to USIL are scheduled on a Tuesday (51 on average). You will have fewer flight options on Saturday, which is when the least amount of flights are scheduled (25 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 November 19, 2025.
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.
Food
7.0
Overall
8.0
Comfort
8.0
Crew
8.6
Entertainment
7.5
Boarding
8.1
Reviews
1 / 20
2.0
MediocreMike,Aug 2025
OKC - AUS
Food
7.0
Overall
8.0
Comfort
8.0
Crew
8.6
Entertainment
7.5
Boarding
8.1
Reviews
1 / 20
2.0
MediocreMike,Aug 2025
OKC - AUS
Food
7.0
Overall
8.0
Comfort
8.0
Crew
8.6
Entertainment
7.5
Boarding
8.1
Reviews
1 / 20
2.0
MediocreMike,Aug 2025
OKC - AUS
Food
7.0
Overall
8.0
Comfort
8.0
Crew
8.6
Entertainment
7.5
Boarding
8.1
Reviews
1 / 20
2.0
MediocreMike,Aug 2025
OKC - AUS
Food
7.0
Overall
8.0
Comfort
8.0
Crew
8.6
Entertainment
7.5
Boarding
8.1
Reviews
1 / 20
2.0
MediocreMike,Aug 2025
OKC - AUS
Food
7.0
Overall
8.0
Comfort
8.0
Crew
8.6
Entertainment
7.5
Boarding
8.1
Reviews
1 / 20
2.0
MediocreMike,Aug 2025
OKC - AUS
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.
Top 5 airlines flying from Colorado to Illinois
Discover the top 5 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 November 19, 2025.
| Airline | Cheapest | Average | Flexibility | On-time |
|---|---|---|---|---|
| Cheapest$66 | Average$175 | FlexibilityNo cancel fee | On-time62% | |
| Cheapest$77 | Average$144 | FlexibilityNo cancel fee | On-time88% | |
| Cheapest$156 | Average$280 | FlexibilityNo cancel fee | On-time63% | |
| Cheapest$157 | Average$434 | FlexibilityNo cancel fee | On-time71% | |
| Cheapest$166 | Average$435 | FlexibilityNo cancel fee | On-time69% |