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$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 2/25. Fares are subject to change and may not be available on all flights or dates of travel.
DEN — ORD
Jan 1 — Jan 81
Thu 1/1
Thu 1/8
1 adult, Economy
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Cheap 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 December 2, 2025.

This Kiwi.com deal was found by Cheapflights users on 12/2. 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 12/248:45 pmDEN - ORD
Nonstop2h 27mFrontier
Fri 1/96:07 pmORD - DEN
1 stop24h 56mFrontier
Deal found 12/2$106
This Super.com deal was found by Cheapflights users on 12/1. 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 12/316:50 amDEN - STL
Nonstop2h 12mFrontier
Wed 1/77:43 pmSTL - DEN
Nonstop2h 32mFrontier
Deal found 12/1$107
This Kiwi.com deal was found by Cheapflights users on 12/1. 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 12/318:45 pmDEN - ORD
Nonstop2h 27mFrontier
Sun 1/410:49 pmORD - DEN
1 stop30h 09mFrontier
Deal found 12/1$112
This Cheapflightsfares deal was found by Cheapflights users on 12/1. 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 12/318:45 pmDEN - ORD
Nonstop2h 27mFrontier
Wed 1/75:29 pmORD - DEN
1 stop30h 30mFrontier
Deal found 12/1$115
This Expedia deal was found by Cheapflights users on 12/1. 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 12/318:45 pmDEN - ORD
Nonstop2h 27mFrontier
Sat 1/36:17 pmORD - DEN
1 stop6h 20mFrontier
Deal found 12/1$116
This Kiwi.com deal was found by Cheapflights users on 11/30. 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 12/248:45 pmDEN - ORD
Nonstop2h 27mFrontier
Sun 1/410:49 pmORD - DEN
1 stop30h 09mFrontier
Deal found 11/30$117
This Cheapflightsfares deal was found by Cheapflights users on 12/1. 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 12/248:45 pmDEN - ORD
Nonstop2h 27mFrontier
Tue 12/301:27 pmORD - DEN
1 stop11h 40mFrontier
Deal found 12/1$120
This Frontier deal was found by Cheapflights users on 11/30. 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 12/258:45 pmDEN - ORD
Nonstop2h 27mFrontier
Sat 1/36:17 pmORD - DEN
1 stop6h 20mFrontier
Deal found 11/30$121
This Frontier deal was found by Cheapflights users on 11/30. 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 12/1611:00 amDEN - STL
1 stop10h 33mFrontier
Wed 12/177:43 pmSTL - DEN
Nonstop2h 32mFrontier
Deal found 11/30$121
This Gotogate deal was found by Cheapflights users on 12/1. 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 Gotogate 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 12/1$122
This Frontier deal was found by Cheapflights users on 12/2. 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 12/177:05 amDEN - STL
Nonstop2h 09mFrontier
Sun 12/2110:10 pmSTL - DEN
1 stop11h 54mFrontier
Deal found 12/2$122
This deal was found by Cheapflights users on 12/2. 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 is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 12/58:45 pmDEN - ORD
Nonstop2h 27mFrontier
Sun 12/77:00 amORD - DEN
Nonstop2h 56mFrontier
Deal found 12/2$126

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 December 2, 2025.

Most accurate provider

CheapOair
3 stars

Most trusted provider

CheapOair
3 stars

Round-trip from

$95
(Kiwi.com)

One-way from

$24
(Frontier)

Popular in

October

Cheapest in

January

Average price

$205

Good round-trip deal

$129 or less

Good one-way deal

$97 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. 3% potential increase in price ($8 potential increase over avg. RT price).
Search Deals
Cheapest flight prices on average. 0% potential price decrease ($2 potential savings vs. average RT price).
Search Deals
Average for round-trip flights in December 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 December 2, 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

DenverChicago

DEN - MDW

DENMDW

Denver Intl

Wed 1/28

6:25 pm-9:50 pm

Nonstop2h 25m

Chicago Midway

Sat 1/31

9:45 am-1:15 pm

1 stop4h 30m

$136

DenverChicago

DEN - MDW

DENMDW

Denver Intl

Fri 1/9

6:25 pm-9:50 pm

Nonstop2h 25m

Chicago Midway

Mon 1/12

7:55 pm-9:40 pm

Nonstop2h 45m

$149

DenverChicago

DEN - MDW

DENMDW

Denver Intl

Tue 1/20

6:25 pm-9:50 pm

Nonstop2h 25m

Chicago Midway

Sat 1/24

7:40 pm-9:25 pm

Nonstop2h 45m

$151

DenverChicago

DEN - ORD

DENORD

Denver Intl

Wed 1/7

6:00 am-9:44 am

Nonstop2h 44m

Chicago O'Hare Intl

Wed 1/7

2:36 pm-4:34 pm

Nonstop2h 58m

$163

Colorado SpringsChicago

COS - MDW

COSMDW

Colorado Springs

Wed 1/21

1:45 pm-8:40 pm

1 stop5h 55m

Chicago Midway

Wed 2/4

8:15 am-1:05 pm

1 stop5h 50m

$166

DenverChicago

DEN - MDW

DENMDW

Denver Intl

Thu 1/15

7:05 pm-10:25 pm

Nonstop2h 20m

Chicago Midway

Mon 1/19

11:20 am-1:05 pm

Nonstop2h 45m

$171

Colorado SpringsChicago

COS - ORD

COSORD

Colorado Springs

Sat 2/7

11:43 am-3:35 pm

Nonstop2h 52m

Chicago O'Hare Intl

Sat 2/14

2:40 pm-6:20 pm

1 stop4h 40m

$173

DenverSt. Louis

DEN - STL

DENSTL

Denver Intl

Sat 1/24

9:45 am-12:55 pm

Nonstop2h 10m

Lambert-St Louis

Mon 1/26

5:50 pm-10:40 pm

1 stop5h 50m

$173

DenverChicago

DEN - ORD

DENORD

Denver Intl

Tue 1/6

6:00 am-9:43 am

Nonstop2h 43m

Chicago O'Hare Intl

Sat 1/10

2:15 pm-4:12 pm

Nonstop2h 57m

$175

DenverChicago

DEN - ORD

DENORD

Denver Intl

Wed 1/7

5:42 pm-9:15 pm

Nonstop2h 33m

Chicago O'Hare Intl

Sat 1/17

12:53 pm-2:51 pm

Nonstop2h 58m

$175

Flights are sorted by cheapest round-trip flights first.

Deals found on 12/2

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 December 2, 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 38% 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 29, 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 December 2, 2025.

The most flights from USCO to USIL are scheduled on a Tuesday (44 on average). You will have fewer flight options on Wednesday, which is when the least amount of flights are scheduled (19 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 December 2, 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
4,253 reviews

Comfort

8.0

Boarding

8.1

Crew

8.6

Food

7.0

Overall

8.0

Entertainment

7.5

Reviews

1 / 20
10.0
Excellent

William Drew,Nov 2025

SJC - HNL

Flight crew was amazing! Usually they're very good on Southwest, but this crew went above and beyond. I have never ever seen so many rounds of drink service on a flight before.
Southwest
8.0
Very good
4,253 reviews
Southwest
8.0
Very good
4,253 reviews

Comfort

8.0

Boarding

8.1

Crew

8.6

Food

7.0

Overall

8.0

Entertainment

7.5

Reviews

1 / 20
10.0
Excellent

William Drew,Nov 2025

SJC - HNL

Flight crew was amazing! Usually they're very good on Southwest, but this crew went above and beyond. I have never ever seen so many rounds of drink service on a flight before.
United Airlines
7.4
Good
9,063 reviews
Southwest
8.0
Very good
4,253 reviews

Comfort

8.0

Boarding

8.1

Crew

8.6

Food

7.0

Overall

8.0

Entertainment

7.5

Reviews

1 / 20
10.0
Excellent

William Drew,Nov 2025

SJC - HNL

Flight crew was amazing! Usually they're very good on Southwest, but this crew went above and beyond. I have never ever seen so many rounds of drink service on a flight before.
American Airlines
7.2
Good
11,043 reviews
Southwest
8.0
Very good
4,253 reviews

Comfort

8.0

Boarding

8.1

Crew

8.6

Food

7.0

Overall

8.0

Entertainment

7.5

Reviews

1 / 20
10.0
Excellent

William Drew,Nov 2025

SJC - HNL

Flight crew was amazing! Usually they're very good on Southwest, but this crew went above and beyond. I have never ever seen so many rounds of drink service on a flight before.
Allegiant Air
7.2
Good
698 reviews
Southwest
8.0
Very good
4,253 reviews

Comfort

8.0

Boarding

8.1

Crew

8.6

Food

7.0

Overall

8.0

Entertainment

7.5

Reviews

1 / 20
10.0
Excellent

William Drew,Nov 2025

SJC - HNL

Flight crew was amazing! Usually they're very good on Southwest, but this crew went above and beyond. I have never ever seen so many rounds of drink service on a flight before.
Frontier
5.8
Fair
3,094 reviews
Southwest
8.0
Very good
4,253 reviews

Comfort

8.0

Boarding

8.1

Crew

8.6

Food

7.0

Overall

8.0

Entertainment

7.5

Reviews

1 / 20
10.0
Excellent

William Drew,Nov 2025

SJC - HNL

Flight crew was amazing! Usually they're very good on Southwest, but this crew went above and beyond. I have never ever seen so many rounds of drink service on a flight before.

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 Southwest, United Airlines, and Delta fly from Colorado to Illinois in about 2h 25m. The time it takes to get you to your destination can typically vary by up to 2h 42m. Colorado and Illinois are separated by a distance of 893 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 Frontier, with whom users have recently found tickets for as low as $36. However, be on the lookout for offers from Allegiant Air and Southwest, 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 December 2, 2025.
AirlineCheapestAverageFlexibilityOn-time
FrontierCheapest$64Average$174FlexibilityNo cancel feeOn-time62%
Allegiant AirCheapest$77Average$143FlexibilityNo cancel feeOn-time88%
SouthwestCheapest$155Average$279FlexibilityNo cancel feeOn-time63%
American AirlinesCheapest$156Average$436FlexibilityNo cancel feeOn-time71%
United AirlinesCheapest$165Average$428FlexibilityNo cancel feeOn-time69%

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