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$35+ 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 12/15. Fares are subject to change and may not be available on all flights or dates of travel.
DEN — ORD
nov. 27 — dic. 41
jue. 11/27
jue. 12/4
1 adult, Economy
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Find flight deals from Colorado to Illinois

Cheapest flights from Colorado to Illinois
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 octubre 28, 2025.

This Kiwi.com deal was found by Cheapflights users on 10/27. Clicking the “Pick Dates” 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.
mar. 11/116:00 amDEN - STL
Nonstop2h 07mFrontier
sáb. 11/157:45 pmSTL - DEN
Nonstop2h 28mFrontier
Deal found 10/27$101
This CheapOair deal was found by Cheapflights users on 10/26. Clicking the “Pick Dates” 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.
jue. 12/411:59 pmDEN - STL
1 stop21h 34mFrontier
sáb. 12/67:43 pmSTL - DEN
Nonstop2h 32mFrontier
Deal found 10/26$102
This Frontier deal was found by Cheapflights users on 10/26. Clicking the “Pick Dates” 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.
sáb. 12/67:05 amDEN - STL
Nonstop2h 09mFrontier
lun. 12/83:30 pmSTL - DEN
1 stop29h 43mFrontier
Deal found 10/26$103
This CheapOair deal was found by Cheapflights users on 10/25. Clicking the “Pick Dates” 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.
sáb. 11/86:00 amDEN - STL
1 stop8h 56mFrontier
sáb. 11/154:33 pmSTL - DEN
1 stop7h 43mFrontier
Deal found 10/25$110
This Kiwi.com deal was found by Cheapflights users on 10/28. Clicking the “Pick Dates” 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.
mar. 11/116:00 amDEN - STL
Nonstop2h 07mFrontier
vie. 11/147:45 pmSTL - DEN
Nonstop2h 28mFrontier
Deal found 10/28$111
This Frontier deal was found by Cheapflights users on 10/26. Clicking the “Pick Dates” 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.
vie. 11/146:00 amDEN - STL
Nonstop2h 07mFrontier
mar. 11/187:45 pmSTL - DEN
Nonstop2h 28mFrontier
Deal found 10/26$112
This Booking.com deal was found by Cheapflights users on 10/27. Clicking the “Pick Dates” 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.
dom. 12/147:33 amDEN - STL
1 stop27h 39mFrontier
lun. 12/157:43 pmSTL - DEN
Nonstop2h 32mFrontier
Deal found 10/27$113
This Frontier deal was found by Cheapflights users on 10/28. Clicking the “Pick Dates” 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.
jue. 12/258:45 pmDEN - ORD
Nonstop2h 27mFrontier
jue. 1/17:00 amORD - DEN
Nonstop2h 56mFrontier
Deal found 10/28$115
This CheapOair deal was found by Cheapflights users on 10/28. Clicking the “Pick Dates” 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.
mié. 12/107:05 amDEN - STL
Nonstop2h 09mFrontier
dom. 12/141:16 pmSTL - DEN
1 stop15h 42mFrontier
Deal found 10/28$115
This Frontier deal was found by Cheapflights users on 10/26. Clicking the “Pick Dates” 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.
lun. 11/1012:59 amDEN - ORD
1 stop9h 15mFrontier
lun. 11/176:00 amORD - DEN
Nonstop2h 41mFrontier
Deal found 10/26$116
This Frontier deal was found by Cheapflights users on 10/27. Clicking the “Pick Dates” 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.
lun. 11/108:05 amDEN - MDW
Nonstop2h 25mFrontier
sáb. 11/151:37 pmMDW - DEN
1 stop7h 22mFrontier
Deal found 10/27$116
This CheapOair deal was found by Cheapflights users on 10/28. Clicking the “Pick Dates” 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.
vie. 12/57:05 amDEN - STL
Nonstop2h 09mFrontier
lun. 12/812:07 pmSTL - DEN
1 stop7h 01mFrontier
Deal found 10/28$116

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 octubre 28, 2025.

Most accurate provider

CheapOair
3 stars

Most trusted provider

CheapOair
3 stars

Round-trip from

$101
(Kiwi.com)

One-way from

$35
(Cheapflightsfares)

Popular in

May

Cheapest in

February

Average price

$217

Good round-trip deal

$166 or less

Good one-way deal

$100 or less
Provider with most accurate pricing for Denver Intl-Chicago (CHI) flight deals.
Search Deals
Provider most trusted by Cheapflights users for Denver Intl-Chicago (CHI) flights.
Search Deals
From Colorado to Illinois
Search Deals
One-way flight from Colorado to Illinois
Search Deals
Highest demand for flights based on searches. 6% potential increase in price ($14 potential increase over avg. RT price).
Search Deals
Cheapest flight prices on average. 0% potential price decrease ($3 potential savings vs. average RT price).
Search Deals
Average for round-trip flights in October 2025
Search Deals
Price to beat on a round-trip flight from Colorado to Illinois.
Search Deals
Price to beat on a one-way flight from Colorado to Illinois.
Search Deals

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 octubre 28, 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

DenverSt. Louis

DEN - STL

DENSTL

Denver Intl

vie. 12/12

7:05 am-10:14 am

Nonstop2h 09m

Lambert-St Louis

dom. 12/14

9:54 am-8:24 am

1 stop23h 30m

$149

DenverChicago

DEN - MDW

DENMDW

Denver Intl

vie. 1/16

5:25 am-8:55 am

Nonstop2h 30m

Chicago Midway

lun. 1/19

9:55 am-2:30 pm

1 stop5h 35m

$186

DenverChicago

DEN - ORD

DENORD

Denver Intl

mié. 11/26

12:55 am-8:57 am

1 stop7h 02m

Chicago O'Hare Intl

mar. 12/2

11:00 am-3:39 pm

1 stop5h 39m

$197

DenverChicago

DEN - ORD

DENORD

Denver Intl

mié. 12/10

5:45 am-3:20 pm

1 stop8h 35m

Chicago O'Hare Intl

mié. 12/17

8:50 am-12:53 pm

1 stop5h 03m

$197

DenverChicago

DEN - MDW

DENMDW

Denver Intl

mié. 12/3

4:45 pm-8:05 pm

Nonstop2h 20m

Chicago Midway

vie. 12/5

12:20 pm-1:55 pm

Nonstop2h 35m

$197

DenverChicago

DEN - ORD

DENORD

Denver Intl

jue. 12/25

6:45 am-12:54 pm

1 stop5h 09m

Chicago O'Hare Intl

mar. 1/6

8:50 am-2:02 pm

1 stop6h 12m

$197

DenverChicago

DEN - ORD

DENORD

Denver Intl

vie. 1/23

12:30 am-10:15 am

1 stop8h 45m

Chicago O'Hare Intl

mié. 2/4

5:54 pm-12:28 am

1 stop7h 34m

$197

DenverChicago

DEN - ORD

DENORD

Denver Intl

vie. 1/16

6:05 am-1:07 pm

1 stop6h 02m

Chicago O'Hare Intl

sáb. 1/17

6:50 am-1:35 pm

1 stop7h 45m

$197

DenverChicago

DEN - MDW

DENMDW

Denver Intl

mié. 12/10

4:44 pm-11:47 pm

1 stop6h 03m

Chicago Midway

mié. 12/17

9:59 am-3:39 pm

1 stop6h 40m

$197

DenverChicago

DEN - MDW

DENMDW

Denver Intl

vie. 1/16

7:05 pm-10:25 pm

Nonstop2h 20m

Chicago Midway

sáb. 1/17

9:45 am-1:50 pm

1 stop5h 05m

$207

Flights are sorted by cheapest round-trip flights first.

Deals found on 10/27

Showing 1-10 of 60 results
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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 octubre 28, 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 October 26, 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.

How much does it cost to fly round-trip from Colorado to Illinois?

Reviews of airlines servicing Illinois

Get insights into the airlines that provide service to Illinois. Read reviews, discover amenities, and learn about the overall travel experience offered by airlines. Use this information to make informed decisions when choosing an airline for your flight to Illinois. Reviews last updated octubre 28, 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.
Southwest
8.0
Very good
4,235 reviews

Crew

8.6

Entertainment

7.5

Overall

8.0

Boarding

8.1

Comfort

8.0

Food

7.0

Reviews

1 / 20
2.0
Mediocre

Mike,Aug 2025

OKC - AUS

AC was not adequate, even on a night flight. WiFi subpar even for the airlines
Southwest
8.0
Very good
4,235 reviews
Southwest
8.0
Very good
4,235 reviews

Crew

8.6

Entertainment

7.5

Overall

8.0

Boarding

8.1

Comfort

8.0

Food

7.0

Reviews

1 / 20
2.0
Mediocre

Mike,Aug 2025

OKC - AUS

AC was not adequate, even on a night flight. WiFi subpar even for the airlines
United Airlines
7.4
Good
8,996 reviews
Southwest
8.0
Very good
4,235 reviews

Crew

8.6

Entertainment

7.5

Overall

8.0

Boarding

8.1

Comfort

8.0

Food

7.0

Reviews

1 / 20
2.0
Mediocre

Mike,Aug 2025

OKC - AUS

AC was not adequate, even on a night flight. WiFi subpar even for the airlines
American Airlines
7.2
Good
11,033 reviews
Southwest
8.0
Very good
4,235 reviews

Crew

8.6

Entertainment

7.5

Overall

8.0

Boarding

8.1

Comfort

8.0

Food

7.0

Reviews

1 / 20
2.0
Mediocre

Mike,Aug 2025

OKC - AUS

AC was not adequate, even on a night flight. WiFi subpar even for the airlines
Allegiant Air
7.2
Good
695 reviews
Southwest
8.0
Very good
4,235 reviews

Crew

8.6

Entertainment

7.5

Overall

8.0

Boarding

8.1

Comfort

8.0

Food

7.0

Reviews

1 / 20
2.0
Mediocre

Mike,Aug 2025

OKC - AUS

AC was not adequate, even on a night flight. WiFi subpar even for the airlines
Frontier
5.8
Fair
3,122 reviews
Southwest
8.0
Very good
4,235 reviews

Crew

8.6

Entertainment

7.5

Overall

8.0

Boarding

8.1

Comfort

8.0

Food

7.0

Reviews

1 / 20
2.0
Mediocre

Mike,Aug 2025

OKC - AUS

AC was not adequate, even on a night flight. WiFi subpar even for the airlines

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.

  • How long is the flight from Colorado to Illinois?

    Airlines like Frontier, Southwest, and Delta fly from Colorado to Illinois in about 2h 09m. The time it takes to get you to your destination can typically vary by up to 4h 53m. Colorado and Illinois are separated by a distance of 767 mi. When browsing for deals, the options you’ll see will be for both nonstop flights and flights with stops.

  • What are the cheapest airlines to fly from Colorado to Illinois one-way?

    The cheapest airline one-way is United Airlines, with whom users have recently found tickets for as low as $78. However, be on the lookout for offers from Southwest and Frontier, as they are both options that can get you from Colorado to Illinois for a low price.

  • Can I find deals for flights from Colorado to Illinois that include hotel bookings?

    Yes. In addition to deals on Colorado to Illinois flights, Cheapflights offers vacation packages that include both flights and hotel.

  • How can I find direct flights from Colorado to Illinois?

    After entering your origin and destination, apply the non-stop filter on the search result page to find direct flights from Colorado to Illinois.

  • Can I find deals for business class flights from Colorado to Illinois?

    Yes. Cheapflights offers flight deals from Colorado to Illinois by cabin class. In addition to browsing deals, you can also filter by cabin class on the search results page after making a search.

  • 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.

See more FAQs

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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.
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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 octubre 28, 2025.
AirlineCheapestAverageFlexibilityOn-time
FrontierCheapest$65Average$172FlexibilityNo cancel feeOn-time62%
Allegiant AirCheapest$77Average$142FlexibilityNo cancel feeOn-time88%
SouthwestCheapest$155Average$281FlexibilityNo cancel feeOn-time63%
American AirlinesCheapest$157Average$436FlexibilityNo cancel feeOn-time71%
United AirlinesCheapest$166Average$436FlexibilityNo cancel feeOn-time69%

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