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$71+ 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 10/8. Fares are subject to change and may not be available on all flights or dates of travel.
DEN — ORD
Jun 17 — Jun 241
Tue 6/17
Tue 6/24
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 June 12, 2025.

Round-trip from

$102
(Cheapflightsfares)

One-way from

$73
(Kiwi.com)

Popular in

May

Cheapest in

September

Average price

$213

Good round-trip deal

$81 or less

Good one-way deal

$79 or less
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. 12% potential increase in price ($27 potential increase over avg. RT price).
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Cheapest flight prices on average. 1% potential price decrease ($4 potential savings vs. average RT price).
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Average for round-trip flights in June 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 June 12, 2025.

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.
Fri 8/156:31 pmDEN - PIA
Nonstop2h 00mAllegiant Air
Mon 8/184:16 pmPIA - DEN
Nonstop2h 25mAllegiant Air
Deal found 6/11$102
This Frontier deal was found by Cheapflights users on 6/10. 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 9/126:00 amDEN - STL
Nonstop2h 07mFrontier
Thu 9/187:52 pmSTL - DEN
Nonstop2h 28mFrontier
Deal found 6/10$129
This Cheapflightsfares deal was found by Cheapflights users on 6/10. 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 7/38:21 pmDEN - ORD
Nonstop2h 38mFrontier
Sat 7/57:00 amORD - DEN
Nonstop2h 53mFrontier
Deal found 6/10$159
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.
Fri 9/57:10 pmDEN - MDW
Nonstop2h 28mFrontier
Sun 9/77:56 pmMDW - DEN
Nonstop2h 44mFrontier
Deal found 6/12$162
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 8/142:10 pmDEN - STL
1 stop3h 25mSouthwest
Mon 8/186:40 pmSTL - DEN
Nonstop2h 20mSouthwest
Deal found 6/12$163
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 8/61:15 pmDEN - ORD
Nonstop2h 30mSouthwest
Tue 8/123:10 pmORD - DEN
1 stop8h 25mSouthwest
Deal found 6/11$167
This Southwest deal was found by Cheapflights users on 6/9. 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 8/55:50 amDEN - MDW
Nonstop2h 20mSouthwest
Tue 8/122:45 pmMDW - DEN
1 stop4h 15mSouthwest
Deal found 6/9$167
This American 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 American Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 8/25:36 pmDEN - ORD
Nonstop2h 45mAmerican Airlines
Tue 8/59:50 amORD - DEN
Nonstop2h 41mAmerican Airlines
Deal found 6/11$177
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.
Wed 9/2411:59 pmDEN - STL
1 stop7h 06mAmerican Airlines
Mon 9/293:57 pmSTL - DEN
1 stop6h 04mAmerican Airlines
Deal found 6/12$177
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.
Sun 7/207:50 amDEN - ORD
Nonstop2h 35mUnited Airlines
Tue 7/229:32 pmORD - DEN
Nonstop2h 50mUnited Airlines
Deal found 6/11$189
This Delta deal was found by Cheapflights users on 6/10. 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 9/1512:59 amDEN - STL
1 stop6h 11mDelta
Mon 9/225:30 pmSTL - DEN
1 stop6h 00mDelta
Deal found 6/10$197
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.
Tue 8/512:55 amDEN - ORD
1 stop5h 54mDelta
Mon 8/115:30 pmORD - DEN
1 stop7h 45mDelta
Deal found 6/12$217

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 12, 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 8/15

6:31 pm-9:31 pm

Nonstop2h 00m

Greater Peoria

Mon 8/18

4:16 pm-5:41 pm

Nonstop2h 25m

$102

DenverSt. Louis

DEN - STL

DENSTL

Denver Intl

Fri 9/12

6:00 am-9:07 am

Nonstop2h 07m

Lambert-St Louis

Thu 9/18

7:52 pm-9:20 pm

Nonstop2h 28m

$129

DenverChicago

DEN - ORD

DENORD

Denver Intl

Thu 8/28

5:32 pm-9:18 pm

Nonstop2h 46m

Chicago O'Hare Intl

Mon 9/1

11:50 am-1:25 pm

Nonstop2h 35m

$158

DenverChicago

DEN - ORD

DENORD

Denver Intl

Thu 7/3

8:21 pm-11:59 pm

Nonstop2h 38m

Chicago O'Hare Intl

Sat 7/5

7:00 am-8:53 am

Nonstop2h 53m

$159

DenverChicago

DEN - MDW

DENMDW

Denver Intl

Fri 9/5

7:10 pm-10:38 pm

Nonstop2h 28m

Chicago Midway

Sun 9/7

7:56 pm-9:40 pm

Nonstop2h 44m

$162

DenverSt. Louis

DEN - STL

DENSTL

Denver Intl

Thu 8/14

2:10 pm-6:35 pm

1 stop3h 25m

Lambert-St Louis

Mon 8/18

6:40 pm-8:00 pm

Nonstop2h 20m

$163

DenverChicago

DEN - ORD

DENORD

Denver Intl

Mon 8/11

5:00 am-1:05 pm

1 stop7h 05m

Chicago O'Hare Intl

Wed 8/13

7:00 am-8:40 am

Nonstop2h 40m

$167

DenverChicago

DEN - MDW

DENMDW

Denver Intl

Tue 8/5

5:50 am-9:10 am

Nonstop2h 20m

Chicago Midway

Tue 8/12

2:45 pm-6:00 pm

1 stop4h 15m

$167

DenverSt. Louis

DEN - STL

DENSTL

Denver Intl

Wed 9/24

11:59 pm-8:05 am

1 stop7h 06m

Lambert-St Louis

Mon 9/29

3:57 pm-9:01 pm

1 stop6h 04m

$177

DenverSt. Louis

DEN - STL

DENSTL

Denver Intl

Mon 9/15

12:59 am-8:10 am

1 stop6h 11m

Lambert-St Louis

Mon 9/22

5:30 pm-10:30 pm

1 stop6h 00m

$197

Flights are sorted by cheapest round-trip flights first.

Deals found on 6/11

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, 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 June 12, 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 June 12, 2025.

The most flights from USCO to USIL are scheduled on a Monday (67 on average). You will have fewer flight options on Saturday, which is when the least amount of flights are scheduled (49 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 June 12, 2025.
Read through reviews of airlines operating flights from Colorado to Illinois, such as Alaska Airlines, Southwest and Delta. Reviews also offer insight into each airline's entertainment options, comfort, food, crew/service, and boarding process.
Alaska Airlines
8.0
Very good
10,000 reviews

Food

7.1

Boarding

8.1

Entertainment

7.1

Overall

8.0

Comfort

7.8

Crew

8.5

Reviews

1 / 20
10.0
Excellent

James,Apr 2025

LAX - SFO

Good flight except the uncontrollable cold air from the ceiling.
Alaska Airlines
8.0
Very good
10,000 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Food

7.1

Boarding

8.1

Entertainment

7.1

Overall

8.0

Comfort

7.8

Crew

8.5

Reviews

1 / 20
10.0
Excellent

James,Apr 2025

LAX - SFO

Good flight except the uncontrollable cold air from the ceiling.
Southwest
8.0
Very good
4,287 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Food

7.1

Boarding

8.1

Entertainment

7.1

Overall

8.0

Comfort

7.8

Crew

8.5

Reviews

1 / 20
10.0
Excellent

James,Apr 2025

LAX - SFO

Good flight except the uncontrollable cold air from the ceiling.
Delta
8.0
Very good
7,950 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Food

7.1

Boarding

8.1

Entertainment

7.1

Overall

8.0

Comfort

7.8

Crew

8.5

Reviews

1 / 20
10.0
Excellent

James,Apr 2025

LAX - SFO

Good flight except the uncontrollable cold air from the ceiling.
United Airlines
7.4
Good
8,790 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Food

7.1

Boarding

8.1

Entertainment

7.1

Overall

8.0

Comfort

7.8

Crew

8.5

Reviews

1 / 20
10.0
Excellent

James,Apr 2025

LAX - SFO

Good flight except the uncontrollable cold air from the ceiling.
Allegiant Air
7.3
Good
725 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Food

7.1

Boarding

8.1

Entertainment

7.1

Overall

8.0

Comfort

7.8

Crew

8.5

Reviews

1 / 20
10.0
Excellent

James,Apr 2025

LAX - SFO

Good flight except the uncontrollable cold air from the ceiling.

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 $73. However, be on the lookout for offers from American 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 June 12, 2025.
AirlineCheapestAverageFlexibilityOn-time
FrontierCheapest$54Average$162FlexibilityNo cancel feeOn-time62%
Allegiant AirCheapest$84Average$164FlexibilityNo cancel feeOn-time88%
American AirlinesCheapest$149Average$479FlexibilityNo cancel feeOn-time71%
SouthwestCheapest$155Average$293FlexibilityNo cancel feeOn-time63%
United AirlinesCheapest$156Average$447FlexibilityNo cancel feeOn-time69%

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