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$76+ 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 11/2. Fares are subject to change and may not be available on all flights or dates of travel.
DEN — ORD
Jul 6 — Jul 131
Sun 7/6
Sun 7/13
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 July 1, 2025.

Round-trip from

$99
(Gotogate)

One-way from

$76
(Mytrip)

Popular in

May

Cheapest in

September

Average price

$205

Good round-trip deal

$186 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 July 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 July 1, 2025.

This Gotogate deal was found by Cheapflights users on 6/29. 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 8/156:31 pmDEN - PIA
Nonstop2h 00mAllegiant Air
Mon 8/184:16 pmPIA - DEN
Nonstop2h 25mAllegiant Air
Deal found 6/29$99
This FlightHub deal was found by Cheapflights users on 6/30. 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 FlightHub is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 10/88:44 pmDEN - STL
1 stop11h 08mFrontier
Sun 10/127:52 pmSTL - DEN
Nonstop2h 28mFrontier
Deal found 6/30$137
This FlightHub deal was found by Cheapflights users on 7/1. 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 FlightHub is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 7/156:30 amDEN - ORD
1 stop8h 44mFrontier
Wed 7/167:00 amORD - DEN
Nonstop2h 53mFrontier
Deal found 7/1$155
This FlightHub deal was found by Cheapflights users on 6/30. 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 FlightHub is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 8/159:15 pmDEN - MDW
1 stop15h 35mFrontier
Mon 8/1812:35 pmMDW - DEN
Nonstop2h 44mFrontier
Deal found 6/30$155
This American Airlines deal was found by Cheapflights users on 6/30. 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 American Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 8/77:22 amDEN - ORD
Nonstop2h 31mAmerican Airlines
Thu 8/76:35 pmORD - DEN
Nonstop2h 47mAmerican Airlines
Deal found 6/30$157
This Southwest deal was found by Cheapflights users on 6/30. 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 Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 8/288:45 pmDEN - MDW
Nonstop2h 20mSouthwest
Mon 9/17:10 amMDW - DEN
Nonstop2h 35mSouthwest
Deal found 6/30$157
This Southwest deal was found by Cheapflights users on 6/30. 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 Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 8/53:25 pmDEN - STL
1 stop5h 00mSouthwest
Tue 8/123:00 pmSTL - DEN
Nonstop2h 15mSouthwest
Deal found 6/30$167
This Southwest deal was found by Cheapflights users on 6/30. 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 Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 9/161:00 pmDEN - ORD
2 stops7h 30mSouthwest
Thu 9/1812:40 pmORD - DEN
Nonstop2h 40mSouthwest
Deal found 6/30$172
This United Airlines deal was found by Cheapflights users on 6/30. 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 United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 8/146:42 pmDEN - STL
Nonstop2h 08mUnited Airlines
Sun 8/175:15 amSTL - DEN
Nonstop2h 37mUnited Airlines
Deal found 6/30$177
This Southwest deal was found by Cheapflights users on 7/1. 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 Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 9/119:45 amCOS - MDW
Nonstop2h 25mSouthwest
Mon 9/157:45 amMDW - COS
Nonstop2h 25mSouthwest
Deal found 7/1$181
This American Airlines deal was found by Cheapflights users on 6/29. 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.
Tue 8/2612:07 pmCOS - ORD
Nonstop2h 43mAmerican Airlines
Mon 9/19:50 amORD - COS
Nonstop2h 47mAmerican Airlines
Deal found 6/29$181
This United Airlines deal was found by Cheapflights users on 7/1. 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 United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 8/271:55 pmCOS - ORD
1 stop5h 02mUnited Airlines
Mon 9/19:07 amORD - COS
Nonstop2h 49mUnited Airlines
Deal found 7/1$191

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 July 1, 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

$99

DenverSt. Louis

DEN - STL

DENSTL

Denver Intl

Wed 10/8

8:44 pm-8:52 am

1 stop11h 08m

Lambert-St Louis

Sun 10/12

7:52 pm-9:20 pm

Nonstop2h 28m

$137

DenverChicago

DEN - ORD

DENORD

Denver Intl

Tue 7/15

6:30 am-4:14 pm

1 stop8h 44m

Chicago O'Hare Intl

Wed 7/16

7:00 am-8:53 am

Nonstop2h 53m

$155

DenverChicago

DEN - MDW

DENMDW

Denver Intl

Fri 8/15

9:15 pm-1:50 pm

1 stop15h 35m

Chicago Midway

Mon 8/18

12:35 pm-2:19 pm

Nonstop2h 44m

$155

DenverChicago

DEN - ORD

DENORD

Denver Intl

Thu 8/7

7:22 am-10:53 am

Nonstop2h 31m

Chicago O'Hare Intl

Thu 8/7

6:35 pm-8:22 pm

Nonstop2h 47m

$157

DenverChicago

DEN - MDW

DENMDW

Denver Intl

Thu 8/28

8:45 pm-12:05 am

Nonstop2h 20m

Chicago Midway

Sat 8/30

7:25 pm-9:05 pm

Nonstop2h 40m

$157

DenverSt. Louis

DEN - STL

DENSTL

Denver Intl

Tue 8/5

3:25 pm-9:25 pm

1 stop5h 00m

Lambert-St Louis

Tue 8/12

3:00 pm-4:15 pm

Nonstop2h 15m

$167

DenverChicago

DEN - ORD

DENORD

Denver Intl

Tue 9/16

1:00 pm-9:30 pm

2 stops7h 30m

Chicago O'Hare Intl

Thu 9/18

12:40 pm-2:20 pm

Nonstop2h 40m

$172

DenverSt. Louis

DEN - STL

DENSTL

Denver Intl

Thu 8/14

6:42 pm-9:50 pm

Nonstop2h 08m

Lambert-St Louis

Sun 8/17

5:15 am-6:52 am

Nonstop2h 37m

$177

Colorado SpringsChicago

COS - ORD

COSORD

Colorado Springs

Wed 8/27

12:02 pm-3:43 pm

Nonstop2h 41m

Chicago O'Hare Intl

Mon 9/1

9:07 am-10:56 am

Nonstop2h 49m

$181

Flights are sorted by cheapest round-trip flights first.

Deals found on 6/30

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 July 1, 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 July 1, 2025.

The most flights from USCO to USIL are scheduled on a Tuesday (66 on average). You will have fewer flight options on Saturday, which is when the least amount of flights are scheduled (20 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 July 1, 2025.
Read reviews from past customers who have flown Southwest, Delta, and United 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
4,273 reviews

Entertainment

7.6

Food

7.0

Overall

8.0

Crew

8.6

Comfort

8.0

Boarding

8.2

Reviews

1 / 20
8.0
Excellent

John,May 2025

PVD - BNA

It’s southwest so no frills but clean, efficient and got me to my location.
Southwest
8.0
Very good
4,273 reviews
Southwest
8.0
Very good
4,273 reviews

Entertainment

7.6

Food

7.0

Overall

8.0

Crew

8.6

Comfort

8.0

Boarding

8.2

Reviews

1 / 20
8.0
Excellent

John,May 2025

PVD - BNA

It’s southwest so no frills but clean, efficient and got me to my location.
Delta
8.0
Very good
7,973 reviews
Southwest
8.0
Very good
4,273 reviews

Entertainment

7.6

Food

7.0

Overall

8.0

Crew

8.6

Comfort

8.0

Boarding

8.2

Reviews

1 / 20
8.0
Excellent

John,May 2025

PVD - BNA

It’s southwest so no frills but clean, efficient and got me to my location.
United Airlines
7.4
Good
8,858 reviews
Southwest
8.0
Very good
4,273 reviews

Entertainment

7.6

Food

7.0

Overall

8.0

Crew

8.6

Comfort

8.0

Boarding

8.2

Reviews

1 / 20
8.0
Excellent

John,May 2025

PVD - BNA

It’s southwest so no frills but clean, efficient and got me to my location.
American Airlines
7.2
Good
10,000 reviews
Southwest
8.0
Very good
4,273 reviews

Entertainment

7.6

Food

7.0

Overall

8.0

Crew

8.6

Comfort

8.0

Boarding

8.2

Reviews

1 / 20
8.0
Excellent

John,May 2025

PVD - BNA

It’s southwest so no frills but clean, efficient and got me to my location.
Allegiant Air
7.2
Good
710 reviews
Southwest
8.0
Very good
4,273 reviews

Entertainment

7.6

Food

7.0

Overall

8.0

Crew

8.6

Comfort

8.0

Boarding

8.2

Reviews

1 / 20
8.0
Excellent

John,May 2025

PVD - BNA

It’s southwest so no frills but clean, efficient and got me to my location.

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 $76. 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, 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 July 1, 2025.
AirlineCheapestAverageFlexibilityOn-time
FrontierCheapest$54Average$169FlexibilityNo cancel feeOn-time62%
Allegiant AirCheapest$84Average$166FlexibilityNo cancel feeOn-time88%
American AirlinesCheapest$151Average$475FlexibilityNo cancel feeOn-time71%
SouthwestCheapest$155Average$293FlexibilityNo cancel feeOn-time63%
United AirlinesCheapest$159Average$455FlexibilityNo cancel feeOn-time69%

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