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$36+ 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 3/19. Fares are subject to change and may not be available on all flights or dates of travel.
DEN — ORD
Feb 25 — Mar 41
Tue 2/25
Tue 3/4
1 adult, Economy
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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 February 20, 2025.

Most accurate provider

FlightHub
3 stars

Most trusted provider

FlightHub
3 stars

Round-trip from

$72
(Kiwi.com)

One-way from

$36
(Frontier)

Popular in

December

Cheapest in

April

Average price

$174

Good round-trip deal

$99 or less

Good one-way deal

$72 or less
Provider with most accurate pricing for Denver Intl-Chicago (CHI) flight deals.
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Provider most trusted by Cheapflights users for Denver Intl-Chicago (CHI) flights.
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From Colorado to Illinois
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One-way flight from Colorado to Illinois
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Highest demand for flights based on searches. 13% potential increase in price ($25 potential increase over avg. RT price).
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Cheapest flight prices on average. 2% potential price decrease ($4 potential savings vs. average RT price).
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Average for round-trip flights in February 2025
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Price to beat on a round-trip flight from Colorado to Illinois.
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Price to beat on a one-way flight from Colorado to Illinois.
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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 February 20, 2025.

This Kiwi.com deal was found by Cheapflights users on 2/19. 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 2/266:00 amDEN - STL
Nonstop2h 16mFrontier
Fri 2/287:09 pmSTL - DEN
Nonstop2h 28mFrontier
Deal found 2/19$67
This Frontier deal was found by Cheapflights users on 2/19. 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.
Mon 3/248:55 pmDEN - MDW
Nonstop2h 22mFrontier
Sun 3/306:40 amMDW - DEN
Nonstop2h 52mFrontier
Deal found 2/19$77
This Frontier deal was found by Cheapflights users on 2/20. 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 3/79:08 pmDEN - ORD
Nonstop2h 36mFrontier
Tue 3/116:45 amORD - DEN
Nonstop3h 03mFrontier
Deal found 2/20$78
This Mytrip deal was found by Cheapflights users on 2/20. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Mytrip is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 4/115:17 pmDEN - PIA
Nonstop2h 00mAllegiant Air
Mon 4/143:08 pmPIA - DEN
Nonstop2h 19mAllegiant Air
Deal found 2/20$86
This American Airlines deal was found by Cheapflights users on 2/20. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure American Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 4/232:00 pmDEN - ORD
Nonstop2h 33mAmerican Airlines
Sat 4/268:39 pmORD - DEN
Nonstop3h 00mAmerican Airlines
Deal found 2/20$159
This Southwest deal was found by Cheapflights users on 2/20. 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 5/77:25 pmDEN - MDW
Nonstop2h 25mSouthwest
Sat 5/108:35 pmMDW - DEN
Nonstop2h 45mSouthwest
Deal found 2/20$159
This Gotogate deal was found by Cheapflights users on 2/20. 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 3/76:00 amDEN - STL
Nonstop2h 16mMultiple Airlines
Mon 3/106:30 amSTL - DEN
1 stop13h 03mMultiple Airlines
Deal found 2/20$167
This United Airlines deal was found by Cheapflights users on 2/20. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 3/138:55 pmDEN - ORD
Nonstop2h 28mUnited Airlines
Mon 3/179:38 pmORD - DEN
Nonstop2h 52mUnited Airlines
Deal found 2/20$170
This FlightHub deal was found by Cheapflights users on 2/20. 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 FlightHub is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 8/1510:14 amDEN - ORD
1 stop7h 57mMultiple Airlines
Mon 8/185:35 amORD - DEN
Nonstop2h 52mMultiple Airlines
Deal found 2/20$171
This Southwest deal was found by Cheapflights users on 2/19. 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 3/227:55 amDEN - ORD
Nonstop2h 35mSouthwest
Thu 3/275:45 pmORD - DEN
1 stop6h 55mSouthwest
Deal found 2/19$174
This Sun Country Air deal was found by Cheapflights users on 2/20. 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 Sun Country Air is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 3/76:50 pmDEN - STL
1 stop15h 44mSun Country Air
Mon 3/106:30 amSTL - DEN
1 stop13h 03mSun Country Air
Deal found 2/20$210
This United Airlines deal was found by Cheapflights users on 2/20. 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 4/115:50 pmDEN - MLI
Nonstop2h 13mUnited Airlines
Sun 4/138:55 amMLI - DEN
Nonstop2h 35mUnited Airlines
Deal found 2/20$210

Find flights from Colorado to Illinois within your budget

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 February 20, 2025.

Fly from

Colorado

Fly to

Illinois

Route

Depart

Return

Price

DenverSt. Louis

DEN - STL

DENSTL

Denver Intl

Sat 5/24

6:00 am-9:12 am

Nonstop2h 12m

Lambert-St Louis

Wed 5/28

6:55 pm-8:26 pm

Nonstop2h 31m

$72

DenverChicago

DEN - ORD

DENORD

Denver Intl

Mon 3/24

9:08 pm-12:44 am

Nonstop2h 36m

Chicago O'Hare Intl

Sun 3/30

6:50 am-8:53 am

Nonstop3h 03m

$77

DenverChicago

DEN - MDW

DENMDW

Denver Intl

Mon 3/24

8:55 pm-12:17 am

Nonstop2h 22m

Chicago Midway

Sun 3/30

6:40 am-8:32 am

Nonstop2h 52m

$77

DenverPeoria

DEN - PIA

DENPIA

Denver Intl

Fri 4/11

5:17 pm-8:17 pm

Nonstop2h 00m

Greater Peoria

Mon 4/14

3:08 pm-4:27 pm

Nonstop2h 19m

$86

DenverChicago

DEN - ORD

DENORD

Denver Intl

Wed 5/7

1:45 pm-5:31 pm

Nonstop2h 46m

Chicago O'Hare Intl

Sat 5/10

9:20 pm-11:08 pm

Nonstop2h 48m

$159

DenverChicago

DEN - MDW

DENMDW

Denver Intl

Wed 5/7

7:25 pm-10:50 pm

Nonstop2h 25m

Chicago Midway

Sat 5/10

8:35 pm-10:20 pm

Nonstop2h 45m

$159

DenverChicago

DEN - ORD

DENORD

Denver Intl

Thu 4/24

7:30 pm-11:05 pm

Nonstop2h 35m

Chicago O'Hare Intl

Sat 4/26

7:00 am-8:40 am

Nonstop2h 40m

$164

DenverSt. Louis

DEN - STL

DENSTL

Denver Intl

Fri 3/7

6:00 am-9:16 am

Nonstop2h 16m

Lambert-St Louis

Mon 3/10

6:30 am-6:33 pm

1 stop13h 03m

$167

DenverChicago

DEN - ORD

DENORD

Denver Intl

Fri 2/28

6:08 pm-8:56 pm

1 stop25h 48m

Chicago O'Hare Intl

Fri 3/7

6:30 am-8:33 am

Nonstop3h 03m

$203

DenverSt. Louis

DEN - STL

DENSTL

Denver Intl

Fri 3/7

6:50 pm-11:34 am

1 stop15h 44m

Lambert-St Louis

Mon 3/10

6:30 am-6:33 pm

1 stop13h 03m

$210

Flights are sorted by cheapest round-trip flights first.

Deals found on 2/20

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.

Travel insights for flights from Colorado to Illinois

Get recent, data-driven insights about flights from Colorado to Illinois including ideal travel times, pricing trends, and more.

What is the cheapest month to book a flight from Colorado to Illinois?

Currently, August is the cheapest month in which you can book a flight from Colorado to Illinois (average of $245). Flying from Colorado to Illinois in March is currently the most expensive (average of $321). 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 February 20, 2025.

Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Colorado to Illinois as you normally would.

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 February 20, 2025.

The most flights from USCO to USIL are scheduled on a Thursday (48 on average). You will have fewer flight options on Saturday, which is when the least amount of flights are scheduled (15 on average).

Rainfall in Illinois by month

Plan your trip to Illinois by taking into account the average rainfall totals by month.

In terms of precipitation, rainfall in Illinois ranges from 1.7 - 4.9 inches per month. August is typically the wettest month, when rainfall can reach 4.9 in. January is typically the driest time to visit Illinois when rainfall is around 1.7 in.

Temperature in Illinois by month

Plan your trip to Illinois by taking into account the average temperature totals by month.

If weather is an important factor for your trip to Illinois, use this chart to help with planning. For those seeking warmer temperatures, July is the ideal time of year to visit, when temperatures reach an average of 73.4 F. Travelers looking to avoid the cold should look outside of January, when temperatures are typically at their lowest (around 23.0 F).

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 February 20, 2025.
Read through reviews of airlines operating flights from Colorado to Illinois, such as Southwest, Alaska Airlines and Delta. Reviews also offer insight into each airline's entertainment options, comfort, food, crew/service, and boarding process.
Southwest
8.1
Very good
4,411 reviews

Food

7.1

Boarding

8.2

Overall

8.1

Entertainment

7.6

Comfort

8.1

Crew

8.7

Reviews

1 / 20

2.0
Mediocre

Anonymous,Feb 2025

MCO - STL

Cancelled at last minute, SWA unable to assist in formulating alternate plans. Wound up renting a car and driving 13 hours to beat bad weather forecast at home. Not SWA’s fault that there was significant bad weather across the country.

Southwest
8.1
Very good
4,411 reviews
Southwest
8.1
Very good
4,411 reviews

Food

7.1

Boarding

8.2

Overall

8.1

Entertainment

7.6

Comfort

8.1

Crew

8.7

Reviews

1 / 20

2.0
Mediocre

Anonymous,Feb 2025

MCO - STL

Cancelled at last minute, SWA unable to assist in formulating alternate plans. Wound up renting a car and driving 13 hours to beat bad weather forecast at home. Not SWA’s fault that there was significant bad weather across the country.

Alaska Airlines
8.0
Very good
9,697 reviews
Southwest
8.1
Very good
4,411 reviews

Food

7.1

Boarding

8.2

Overall

8.1

Entertainment

7.6

Comfort

8.1

Crew

8.7

Reviews

1 / 20

2.0
Mediocre

Anonymous,Feb 2025

MCO - STL

Cancelled at last minute, SWA unable to assist in formulating alternate plans. Wound up renting a car and driving 13 hours to beat bad weather forecast at home. Not SWA’s fault that there was significant bad weather across the country.

Delta
8.0
Very good
8,219 reviews
Southwest
8.1
Very good
4,411 reviews

Food

7.1

Boarding

8.2

Overall

8.1

Entertainment

7.6

Comfort

8.1

Crew

8.7

Reviews

1 / 20

2.0
Mediocre

Anonymous,Feb 2025

MCO - STL

Cancelled at last minute, SWA unable to assist in formulating alternate plans. Wound up renting a car and driving 13 hours to beat bad weather forecast at home. Not SWA’s fault that there was significant bad weather across the country.

JetBlue
7.4
Good
3,070 reviews
Southwest
8.1
Very good
4,411 reviews

Food

7.1

Boarding

8.2

Overall

8.1

Entertainment

7.6

Comfort

8.1

Crew

8.7

Reviews

1 / 20

2.0
Mediocre

Anonymous,Feb 2025

MCO - STL

Cancelled at last minute, SWA unable to assist in formulating alternate plans. Wound up renting a car and driving 13 hours to beat bad weather forecast at home. Not SWA’s fault that there was significant bad weather across the country.

United Airlines
7.4
Good
8,765 reviews
Southwest
8.1
Very good
4,411 reviews

Food

7.1

Boarding

8.2

Overall

8.1

Entertainment

7.6

Comfort

8.1

Crew

8.7

Reviews

1 / 20

2.0
Mediocre

Anonymous,Feb 2025

MCO - STL

Cancelled at last minute, SWA unable to assist in formulating alternate plans. Wound up renting a car and driving 13 hours to beat bad weather forecast at home. Not SWA’s fault that there was significant bad weather across the country.

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.

  • 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 United Airlines 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, August is the cheapest month in which you can book a flight from Colorado to Illinois (average of $245). Flying from Colorado to Illinois in March is currently the most expensive (average of $321). 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 February 20, 2025.
AirlineCheapestAverageFlexibilityOn-time
FrontierCheapest$42Average$142FlexibilityNo cancel feeOn-time62%
Allegiant AirCheapest$84Average$163FlexibilityNo cancel feeOn-time88%
American AirlinesCheapest$139Average$456FlexibilityNo cancel feeOn-time71%
United AirlinesCheapest$145Average$443FlexibilityNo cancel feeOn-time69%
SouthwestCheapest$155Average$314FlexibilityNo cancel feeOn-time63%
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