$33 Find Cheap Flights from Illinois to Colorado

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Low seasonApril
High seasonJuly
Cheapest flight$33
Best time to beat the crowds with an average 10% drop in price.
Most popular time to fly with an average 2% increase in price.
Flight from St. Louis to Denver

FAQs for booking flights from Illinois to Colorado

  • How does KAYAK find such low prices on flights from Illinois to Colorado?

    KAYAK is a travel search engine. That means we look across the web to find the best prices we can find for our users. With over 2 billion flight queries processed yearly, we are able to display a variety of prices and options on flights from Illinois to Colorado.

  • How does KAYAK's flight Price Forecast tool help me choose the right time to buy my flight ticket from Illinois to Colorado?

    KAYAK’s flight Price Forecast tool uses historical data to determine whether the price for a flight from Illinois to Colorado is likely to change within 7 days, so travelers know whether to wait or book now.

  • What is the Hacker Fare option on flights from Illinois to Colorado?

    Hacker Fares allow you to combine one-way tickets in order to save you money over a traditional round-trip ticket. You could then fly from Illinois to Colorado with an airline and back with another airline.

  • What is KAYAK's "flexible dates" feature and why should I care when looking for a flight from Illinois to Colorado?

    Sometimes travel dates aren't set in stone. If your preferred travel dates have some wiggle room, flexible dates will show you all the options when flying from Illinois to Colorado up to 3 days before/after your preferred dates. You can then pick the flights that suit you best.

  • Which is the cheapest airport to fly into in Colorado?

    Prices will differ depending on the departure airport, but generally, the cheapest airport to fly to in Colorado is Denver Intl Airport (DEN), with an average flight price of $181.

  • What is the cheapest day to fly to Colorado?

    Based on KAYAK data, the cheapest day to fly to Colorado is Friday where round-trip tickets can be as cheap as $245. On the other hand, the most expensive day to fly is Sunday, where round-trip prices are $314 on average.

  • What is the cheapest time of day to fly to Colorado?

    The cheapest time of day to fly to Colorado is generally in the evening, when round-trip flights cost $211 on average. Morning departures are around 25% more expensive than evening flights, on average. The most expensive time of day to fly to Colorado is generally in the afternoon, which is peak travel time and where the average cost of a ticket is $308.

  • What is the cheapest flight to Colorado?

    The cheapest ticket to Colorado from Illinois found in the last 72 hours was to Denver, at $102 round-trip. The most popular route is Bloomington (BMI) to Denver (DEN) and the cheapest round-trip airline ticket found on this route in the last 72 hours was $102.

  • What is the cheapest month to fly from Illinois to Colorado?

    The cheapest month for flights from Illinois to Colorado is November, when tickets cost $152 (return) on average. On the other hand, the most expensive months are December and May, when the average cost of round-trip tickets is $218 and $212 respectively.

  • How far in advance should I book a flight from Illinois to Colorado?

    To get a below average price on the flight from Illinois to Colorado, you should book around 3 weeks before departure. For the absolute cheapest price, our data suggests you should book 5 weeks before departure.

  • How long is the flight to Colorado?

    An average nonstop flight from Illinois to Colorado takes 7h 11m, covering a distance of 930 miles. The shortest route is St. Louis (STL) to Denver (DEN) with an average flight time of 2h 15m.

  • What are the most popular destinations in Colorado?

    Based on KAYAK flight searches, the most popular destination is Denver (89% of total searches to Colorado). The next most popular destinations are Colorado Springs (4%) and Aspen (2%). Searches for flights to Grand Junction (1%), to Montrose (1%) and to Vail (1%) are also popular.

Reviews of the top 5 airlines serving from Illinois to Colorado

 
Need help choosing which airline to fly with from Illinois to Colorado? KAYAK airline reviews give an overall score for each airline based on loads of factors, including comfort, boarding, in-flight entertainment and more, to make your decision easier. See airline scores according to verified KAYAK customer reviews.
8.0
SouthwestOverall score based on 4278 reviews
7.6Entertainment
8.6Crew
8.0Comfort
8.2Boarding
7.0Food
Airline reviews

after landing, we stay 2 hours on the taxi way before reaching the gate The airline and the crew were good though

4.0 OkayAnonymous, Jun 2025MDW - LGA
Read more Southwest reviews

after landing, we stay 2 hours on the taxi way before reaching the gate The airline and the crew were good though

Flights delayed by 4-6 hours. Boarding was a mess and unclear. Bags were not at arrival airport and had never even been put on the plane. No idea when I’ll get them. Don’t fly into Denver!

Southwest is typically delayed, and it gets wearisome. It is no longer a discount airline and you get way less than you pay for when it comes to comfort and Ce.

We sat on the plane on the tarmac for 4 hours.

I'm not a fan of Southwest's model. I don't like the herding style of boarding.

After a 3 hour layover in Denver my flight was delayed over 5 hours! No explanation; no assistance; no offer to provide compensation; no one at Southwest was willing to offer any assistance. 8 hours in the Denver airport - ridiculous!

My flight to Chicago left and landed early. My return flight left two minutes late and arrived 2 minutes late. My seat selections were ideal! There were no snacks going to Chicago and no snacks on the return trip. There are no charging outlets on board.

WiFi on the flight was not working. Thus, entertainment options were limited.

I really like open seating. I hate that I've heard this is going away. This is one of the unique things that makes Southwest my goto choice.

For the first time in a long time we had a flawless experience with Southwest. Both flights were early and no mechanical errors at all. We were shocked and pleasantly surprised 😮.

Very rough getting into denver. my kid threw up it was so rough.

Why wasn't this flight departure scheduled eith another crew so that it could leave on time? When we arrived in Denver we had so little time between flights we had run to the connecting flight. We should received some credit for the inconvenience.

I was supposed to be on business class at first class from Denver back to Miami due to weather changes. I missed my connection and it’s put on a flight to Fort Lauderdale. Instead of honoring my business class/1st class ticket, they put me in coach, but there were two first class seats open. I think it’s absolutely disgusting that I paid for first class $1300 ticket and they put me in economy and they had to open seats available and I have still not been refunded the difference. I ended up having to eat a snack box instead of the meal I was supposed to get and did not get home till 2 AM so I think that’s a little pathetic that I had to live off crackers for dinner And my poor dog ate some cheese and salami. Oh yes, apparently when they switched me to the new flight they forgot to mention I had a service dog

Excellent service despite turbulence during the flight. Flight attendants were remarkable!

Flight attendant moved my bag without notifying me and was rude to me when I asked him about it. There was no reason to move it.

The gate attendant let me walk right by her with a bag too big for the overhead compartment

Food choices were very limited. Taste of the dishes was average.

I liked all the informational texts. I always knew where to go and when .

Received an email the night before showing that there would be seatback entertainment on our flight. We get on and there was no seatback entertainment. And then it was a scramble to try to set up the iPads for the kids before takeoff so they could watch something for the four hour flight.

The reason I don’t fly United. No in seat entertainment for a long flight and inconsistent WiFi and entertainment available from my device.

I wish American Airlines would change the airline industry by loading the plane back to front instead of front to back. Planes would board so much more smoothly and quickly.

Terrible. The flight was delayed two hours due to weather. Then when we got on the plane, the first pilot ended up timing out and we had to wait for a second pilot. Second pile came on board and we tax it out. Had to return back to the gate because of an unruly passenger. Then the copilot timed out. Had to wait for new copilot. Also had to wait for maintenance to check for fuel. Then found out the second pilot timed out and we had to wait for a third pilot. Was ready to go and then needed maintenance again for another issue. In the end, it was 2 o’clock in the morning when they announced that the flight couldn’t go because the third pilot and the second copilot had timed out.

I have long legs, my foot was out in the aisle and when a flight attendant came walking by and I didn't notice, instead of saying "excuse me" or anything like that, she kicked my foot. Extremely rude

Excellent! The gate agents were kind enough to rebook me on an earlier flight saving me from a 6 hour layover. Even my luggage made it despite the fact that the connection was technically too narrow. The flight itself was very comfortable, roomy, and clean. Plenty of space for my carryon items with plugs to charge my phone. After a long international flight of 14 hours, this was an excellent way to end my travels!

One of the best flights I’ve had. So smooth.

Great experience. Flight boarded easily. Departed early. Smooth flight. Great arrival in DC--almost no taxing! Almost direct to gate from runway. Crew was terrific. Same cookies and beverages in main cabin. I did not use the entertainment system on this flight.

Most of the delay was due to weather which is not what was at issue here. One delay was due to a missing flashlight and in the end the flashlight was actually found on the plane. The entertainment system is very limited. Live TV options offer only a few channels that are not very appealing. Boarding and deplaning are always difficult. It just takes too much time to get on and off the plane. On the plus side, I missed my connecting flight, but was easily able to book a later flight from the app while enroute.

You were more on time than United. I'm so over united delays.

The meals were mediocre and the alcohol selection was poor. I enjoyed the selection of movies and other entertainment.

I chatted with the captain before the flight, and similarly during the welcome announcement, he warned of a turbulent flight that may impact the in-flight service. However, once at altitude, he announced that the weather changed and he immediately turned off the seatbelt sign. But it appeared the cabin crew had already decided to take off this flight. They remained seated and then just chatted in the galley. The flight was fully catered, but only first class received service.

Tight! Seats are not designed for those of us who wear extra-large clothes.

The non-stop flight from Grand Rapids was excellent. I neither expected or needed a budget flight and Allegiant made the trip easy and for an affordable price, Arriving at the Mesa Airport (AZA) is a delight compared to the international airport. For our return flight, we were able to arrive 75 minutes before the flight, return the rental car, check our bag and make it to the gate in plenty of time. That would never happen at most airports.

Easiest flights I’ve ever taken. Plane was comfortable without overly crowded seating.

Terrible. Still have not received the refund from them. They sent it to some account that I don't even know. Spoke with costumer service and they are unable to help.

I didn’t like it at all. I miss my second flight because of the delay on Allegiant Air now I m stuck in MCO.

Good, but a bit late on take off after loading. Don't like charging for carry ons!

First time flying with them and will definitely fly again in the future. Crew was so nice and friendly, fought was seamless. They are simple planes, no entertainment, but it’s fine for a short flight or if you have personal devices Rates are competitive, and they did so well with keeping the flight on time after a tropical storm, where other airlines had delays and cancellations.

They boarded passengers that sat in the back of the plane first, making boarding very efficient.

I didn't even take this flight. My plans changed and I couldn't get ahold of customer service and the website kept breaking down during the attempt to change the flight. I wound up taking another airline entirely and eating the cost.

The worst flying experience ever 3 delays. No accommodations. Had to deboard the plane after being delayed.

Flight was late. Missed connecting in Denver. My new flight is more than 24 hours later and I have no room, vouchers, or compensation, and might also be bumped from the one tomorrow.

This was one of the first frontier airline flights this spring that wasn't delayed. It actually left on time. Some of the flight crew did not look happy, they didn't smile when the passengers were boarding or getting off the plane, and the passengers initiated greetings, not the staff. To me this was an odd experience to have with any flight/airline. I had a bad experience booking this flight. The price didn't solidify until late hours into the night. Ever time I purchased the ticket, I either received a denial email or an error because the price has changed, but it was never reflected on the flyfrontier or kayak websites until way after midnight on the date of travel. This caused me anxiety and irritation with the websites. Then I noticed a mishap with my name on my voucher as I went to check in, it was incorrect. When I proceeded to correct it, Frontier had no easy, let alone free, way to remedy it. I couldn't correct my name without a $75 charge, I couldn't cancel my voucher to repurchase it with the correct name without a $100 charge, because it was too close to departure. Then calling frontier was nearly impossible to remedy the situation with a human. It's already difficult to want to choose frontier because of all the upcharges, but you feel kinda trapped into doing so because it's the more affordable airline.

Our flight was cancelled. They could do nothing to help us get another flight that was timely. Because the first leg was cancelled we were unable to get to our connection. We had to book on an entirely different airline for today. So we spent more money, lost a day of vacation and will never fly Frontier again, so the 'we are sorry, here is $100 credit' is a joke since we won't be flying on Frontier.

I liked the turn-style feature at gate 209B at LAX. Very efficient process. The gate staff also made several, clearly directed announcements so I felt very informed.

Seats are uncomfortable but price is good. Guess I can put up with misery for four hours.

The plane failed preflight inspection, so we sat there for 90 mins while they tried to fix it. Ultimately, everything was remedied and we made our connecting flight; instead of a 2 hour layover at the airport, we spent it waiting on the plane.

I loked walking out on the tarmac to board and no first class. I didn't like that they have no snacks or onboard wifi to bide your time.

The seats were extremely hard and uncomfortable. It was disappointing even for a budget airline.

Delayed each time on a round trip with no significant weather interference. Updates to flight times came after the fact. 30 min behind in boarding and board and phone still show an on time departure. Some mysterious extra 300 miles that came so surprising they had to fuel while we were already on board?

Our flight was canceled for no known reason. We weren’t told until we were checking in at 5:00 am. This was after our last flight with Frontier where we sat on the plane for three hours (not an exaggeration) before we took off because of a mechanical issue. We won’t be flying Frontier again.

Book cheap flights from Illinois to Colorado

Recent round-trip flight deals

7/29Tue
nonstopFrontier
2h 53mORD-DEN
7/31Thu
nonstopFrontier
2h 39mDEN-ORD
$89
7/29Tue
1 stopFrontier
10h 38mMDW-DEN
8/4Mon
nonstopFrontier
2h 26mDEN-MDW
$94
8/11Mon
nonstopAllegiant Air
2h 20mPIA-DEN
8/29Fri
nonstopAllegiant Air
2h 00mDEN-PIA
$113
9/12Fri
nonstopAllegiant Air
2h 16mPIA-DEN
9/15Mon
nonstopAllegiant Air
2h 00mDEN-PIA
$118
8/4Mon
nonstopSouthwest
2h 20mSTL-DEN
8/11Mon
1 stopSouthwest
3h 25mDEN-STL
$163
8/13Wed
nonstopAmerican Airlines
2h 47mORD-COS
8/23Sat
nonstopAmerican Airlines
2h 43mCOS-ORD
$181
8/13Wed
nonstopAmerican Airlines
2h 47mORD-COS
8/20Wed
nonstopAmerican Airlines
2h 43mCOS-ORD
$182
8/11Mon
nonstopSouthwest
2h 25mMDW-COS
8/19Tue
nonstopSouthwest
2h 20mCOS-MDW
$197
9/14Sun
1 stopUnited Airlines
5h 27mORD-ASE
9/17Wed
1 stopUnited Airlines
5h 01mASE-ORD
$211
8/16Sat
nonstopUnited Airlines
3h 04mORD-COS
8/19Tue
nonstopUnited Airlines
2h 41mCOS-ORD
$213

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Recent one-way flight deals

11/12Wed
nonstopFrontier
2h 28mSTL-DEN
$33
7/5Sat
nonstopFrontier
2h 53mORD-DEN
$38
8/18Mon
nonstopAllegiant Air
2h 25mPIA-DEN
$53
11/3Mon
nonstopAmerican Airlines
2h 44mORD-DEN
$79
8/5Tue
nonstopSouthwest
2h 35mMDW-DEN
$79
8/21Thu
1 stopSouthwest
3h 25mSTL-DEN
$84
8/22Fri
nonstopAllegiant Air
2h 25mPIA-DEN
$86
8/13Wed
1 stopAmerican Airlines
8h 12mSTL-DEN
$88
11/7Fri
nonstopUnited Airlines
2h 49mORD-DEN
$97
8/6Wed
nonstopUnited Airlines
2h 53mORD-COS
$99

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Last minute flights from Illinois to Colorado

Last minute flight, train and bus deals

7/5Sat
nonstopFrontier
2h 49mMDW-DEN
7/10Thu
nonstopFrontier
2h 28mDEN-MDW
$87
7/5Sat
nonstopFrontier
2h 53mORD-DEN
7/8Tue
nonstopFrontier
2h 39mDEN-ORD
$88
7/2Wed
nonstopAllegiant Air
2h 20mPIA-DEN
7/4Fri
nonstopAllegiant Air
2h 03mDEN-PIA
$153
7/4Fri
nonstopAllegiant Air
2h 20mPIA-DEN
7/7Mon
nonstopAllegiant Air
2h 03mDEN-PIA
$306
7/5Sat
nonstopSouthwest
2h 20mSTL-DEN
7/12Sat
nonstopSouthwest
2h 00mDEN-STL
$307
7/5Sat
nonstopSouthwest
2h 20mSTL-DEN
7/13Sun
nonstopSouthwest
2h 00mDEN-STL
$352
7/5Sat
nonstopUnited Airlines
2h 28mMLI-DEN
7/7Mon
nonstopUnited Airlines
2h 17mDEN-MLI
$404
7/5Sat
multi-stopUnited Airlines
5h 05mMLI-DEN
7/7Mon
nonstopUnited Airlines
2h 17mDEN-MLI
$414
7/5Sat
multi-stopAmerican Airlines
7h 46mMLI-DEN
7/8Tue
multi-stopAmerican Airlines
4h 45mDEN-MLI
$429
7/1Tue
multi-stopAmerican Airlines
5h 06mMLI-DEN
7/12Sat
multi-stopAmerican Airlines
5h 30mDEN-MLI
$449

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Everything you need to know for your flight to Colorado

Cabin class types available on flights to Illinois

Cabin classes available on flights to Illinois. Prices are the lowest found on KAYAK over the last 7 days. Price and availability is not guaranteed.

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