$36 Find Cheap Flights from Colorado to Illinois

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Good to know

Low seasonJanuary
Cheapest flight$36
Best time to beat the crowds with an average 2% drop in price.
Most popular time to fly and prices are also 5% lower on average.
Flight from Denver to St. Louis

Flights from Colorado to Illinois: the best tips from KAYAK users

Insights shared by verified travelers who flew the route from Colorado to Illinois 
AdamFlew with SouthwestDEN-ORDOct 2024
Arriving T5 at ORD on Southwest is often a LONG walk, with no moving walkways going out, to baggage claim / pickup.
BrianFlew with United AirlinesDEN-ORDJan 2024
Big airport. Make sure you have enough time between flights for rest, eating, etc…

FAQs for booking flights from Colorado to Illinois

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

    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 Colorado to Illinois.

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

    KAYAK’s flight Price Forecast tool uses historical data to determine whether the price for a flight from Colorado to Illinois 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 Colorado to Illinois?

    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 Colorado to Illinois 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 Colorado to Illinois?

    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 Colorado to Illinois up to 3 days before/after your preferred dates. You can then pick the flights that suit you best.

  • Which airlines fly most frequently to Illinois?

    Colorado and Illinois are connected by different airlines. The airlines that fly that route the most regularly are United Airlines (124 flights per week), Air Canada (94 flights per week), and Southwest (73 flights per week).

  • How many airports are there in Illinois?

    There are 12 airports in Illinois. The busiest airport is Chicago O'Hare Airport (ORD), with 92% of all flights arriving there.

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

    Prices will differ depending on the departure airport, but generally, the cheapest airport to fly to in Illinois is Chicago O'Hare Intl Airport (ORD), with an average flight price of $209.

  • What is the cheapest day to fly to Illinois?

    Based on KAYAK data, the cheapest day to fly to Illinois is Thursday where round-trip tickets can be as cheap as $304. On the other hand, the most expensive day to fly is Sunday, where round-trip prices are $504 on average.

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

    The cheapest time of day to fly to Illinois is generally at night, when round-trip flights cost $197 on average. Morning departures are around 2% cheaper than evening flights, on average. The most expensive time of day to fly to Illinois is generally in the afternoon, which is peak travel time and where the average cost of a ticket is $619.

  • What is the cheapest flight to Illinois?

    The cheapest ticket to Illinois from Colorado found in the last 72 hours was to Chicago O'Hare Intl Airport, at $105 round-trip. The most popular route is Aspen (ASE) to Chicago O'Hare Intl Airport (ORD) and the cheapest round-trip airline ticket found on this route in the last 72 hours was $105.

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

    The cheapest month for flights from Colorado to Illinois is January, when tickets cost $278 (return) on average. On the other hand, the most expensive months are September and July, when the average cost of round-trip tickets is $494 and $485 respectively.

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

    To get a below average price on the flight from Colorado to Illinois, you should book around 4 weeks before departure, which saves you about 34% compared to booking last minute. For the absolute cheapest price, our data suggests you should book 5 weeks before departure.

  • How many cities have direct flights to Illinois?

    From Colorado, there are direct flights to Illinois from 3 cities. The city with the most direct flights is Denver, with 536 direct flights each week.

  • How many direct flights to Illinois are there each day?

    There are around 87 direct flights from within Colorado to Illinois every day. Most flights (52%) depart in the morning.

  • How many direct flights to Illinois are there each week?

    Each week there are around 606 direct flights from within Colorado to Illinois. The most common day for departures is Sunday, with 16% of flights taking off on this day.

  • How long is the flight to Illinois?

    An average nonstop flight from Colorado to Illinois takes 6h 00m, covering a distance of 927 miles. The shortest route is Denver (DEN) to Peoria (PIA) with an average flight time of 1h 51m.

  • How many long-haul flights are there to Illinois each week?

    There are not any long-haul (6-12 hour flight duration) or medium-haul (3-6 hour flight duration) flights to Illinois. Instead, there are 606 short-haul flights (up to 3 hour flight duration), with the most arriving from Denver.

  • What are the most popular destinations in Illinois?

    Based on KAYAK flight searches, the most popular destination is Chicago (78% of total searches to Illinois). The next most popular destinations are St. Louis (12%) and Moline (6%). Searches for flights to Peoria (2%), to Bloomington (1%) and to Evansville (1%) are also popular.

Reviews of the top 5 airlines serving from Colorado to Illinois

 
Need help choosing which airline to fly with from Colorado to Illinois? 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 4239 reviews
8.0Comfort
7.0Food
8.1Boarding
8.6Crew
7.5Entertainment
Airline reviews

Connecting flight is on time and boarding was a breeze!

10.0 ExcellentGabriel, Sep 2025DEN - SMF
Read more Southwest reviews

Connecting flight is on time and boarding was a breeze!

Excellent. Would encourage Southwest to keep current boarding procedures with free style seating. Makes for a fantastic experience

WiFi did not work. For as outrageous as these flights cost, when they’re advertised with certain services/ features they should be in working order

Worst experience I had on Southwest. Still better than most, but the seating was barely tolerable.

It was okay. The plane was delayed from earlier in the day, but they kept updating the departure time, sometimes later, sometimes earlier. That was stressful. Once we finally got on and took off, it was fine. I was supposed to have a connection in Chicago to Los Angeles, and the time for so late I was rebooked to arrive in LA 3 hours late. The departure time to Chicago later became early enough to have taken my original connection and arrive earlier but that wasn't an option.

Everything was on time. I was disappointed by the front section female, African American flight attendant. I did not see her name tag or would have identified by name not race. As passengers moved to the bathroom early in flight, she would say with a disdainful tone “I have to say the seat belt light is on” then go back to her book. Better trained flight attendants say something like be careful the seat belt light is on.

I would have liked to arrive on time - not 5 hours late!

1.5 hour delay, poor service, no compassion from the crew. Terrible experience

Our flight was diverted from being a non-stop to getting within 150 miles and requiring another plane. We heard 4 or 5 different versions from SW as to why we had to stop, then wait for a replacement plane. Five hour delay, weather did not come up as a single excuse.... communication was not clear and well explained. No one really took charge!

Flight was awfully bumpy and landing was a bit jolting. I was in the restroom when snacks and drinks were served and was not asked if i wanted any. I had to ask for water finally.

Better WiFi. I cannot understand that in 2025, United is so behind on a technology that is now a necessity and still painfully unreliable, slow and keeps disconnecting.

Trip was great. A wild landing in Ottawa with the wind and rain, but the pilot did a great job. Always love flying United.👍

Excellent experience. Starting with the agent at the Premier bag drop who noticed I was very early for my scheduled flight and offered to rebook me on an earlier flight with my seat preference. She would not let me leave the counter until she knew that all of the changes and new boarding pass showed up on my United app. At the gate, the flight boarded quickly such that we departed early and the flight was smooth. We arrived 20 minutes early at ORD and I was able to be home in time for dinner. One of the best flights I've had.

Salina to travers city was great! But the sept 24 Tranverse city was not! Traverse city to chichago was cancelled, i went to Denver & got to Salina 6 hours later!

See previous note about the passenger in Denver who threw my husband's bag out of the overhead bin in order to maker room for his own. And the flight attendant back up the new passenger.

Flight attendant in first class gave poor service (like he didn't want to be there) and food was awful. We sat waiting for gate upon arrival over 45 mins.

Weather delay in Chicago?. No sense of urgency to make connection in Chicago for our connecting flight that wasn't delayed. Connection was missed.

Overall it was good. I missed my connection but I was put on another flight.

Overall a very poor experience - booked premium economy tickets but due to last minute flight delays , all my itinery went for a toss and had to fly economy class with no access to lounge or any compensation by united airlines to make up for the flight delays . i had expected better experience than that from united.

It was fine, definitely older planes with no charging or anything. There’s no entertainment set up on board, but it is nice that they allow you to access the in flight entertainment from your phone without having to pay for the Wi-Fi and they do offer free texting.

It was a typical flight. We had a delay which seems to be the normality now. And we had no in flight service due to conditions.

After we landed we sat on the tarmac for 1.5 hours waiting to get to our gate. Ridiculous.

Terrible. Flight delayed for more than 8 hours with only a $12 meal voucher provided for the inconvenience. The airplane did not have breaks on arrival yet they still made us go through the motions and board on time knowing we could not take off then sit for 40+ minutes before having to get of the time. A complete waste of my time. I cannot believe they can stay business with these shenanigans. I’ll avoid this company like the plague moving forward as the lack of accountability is disgraceful.

This was the best 2 flights I have had with American out of SGF. Great crew both flights.

Excellent - explanations were clear staff was nice and flight was comfortable

Lost bag and 2 days no word leaving for cruise no clothes or stuff

Any flight to ORD after about 2pm this summer has been challenging. Flight was delayed getting in (coming from ORD) and that led to it not leaving before a ground stop due to lightening before they could fuel the plane, and so forth. They made up some time but we were still late in arriving at ORD, and that led to missed connections.

Food was ok, but not as good as I have had before on AA.

Pretty good. The food was just mediocre, the boarding and crew were good.

My flight got switched and my prepaid bag didnt transfer over properly so I paid to check ANOTHER BAG. I was placed in a middle seat and it was just miserable. At least it was a bulkhead row so I had legroom. The flight just never seem3d to end

The crew was great and the flight was very smooth. Can’t really judge food since I did not get any because it costs money. The seat was comfortable for what we bought. Thanks!

Crew was great. No entertainment and food and beverage was for purchase only, even water

It was canceled. The flight wasn’t rescheduled, everyone had to figure out their own new arrangements. They said we would get refunded our original fare and receive an additional $150. We received links for $100 only and they expired before we could activate them.

The plane had originated in Las Vegas at 6:30 in the morning and flew to Moline where we boarded. The flight left around 12:30 PM and there were no boxed snacks available and many of the alcoholic beverages were unavailable. I would find it hard to believe that that many of the passengers coming from Las Vegas at 6:30 in the morning, drank and ate that much of the items. I can only come to the conclusion that someone failed to stock the plane for the round-trip. This is a huge revenue failure for the airline and disappointment for the passengers. The flight crew did not seem happy to be there and did not engage with passengers. Allegiant you can do better.

They did not let my husband on the plane with our service animal at the last minute. Do NOT fly this airline with a service animal!

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.

The single worst check in experience I could imagine. I’ll never do any business with Frontier or any affiliated company

Too many extra fees, uncomfortable, little leg room. Will not recommend this airline.

Frontier is the Walmart of airlines. Frontier has removed adjustability and comfort from their seats to make the flight lighter and save gas. This makes it impossible to sleep on their flights. Their customer service is abysmal. Once, I bought a drink on the plane, and they swiped my credit card on the plane to pay for it. Then I got three weeks of daily notices from my bank telling me they tried to charge the wrong card number over and over again. I tried to call them, but they removed the ability to actually talk to someone that can resolve such a problem from their company to cut corners. The only way to talk to someone in person is to go to the check-in counter at the airport (40 minutes drive from my house). Eventually their system gave up on trying to charge the card, after 21 days of repeated tries. They don't pad their prices even a little to handle customer service issues like missed flights. They also have a blanket policy preventing helping you reschedule a missed flight if their system says you "cancelled" your own flight online. This is a major problem because their website is broken on mobile devices, the only web browser you have at the airport when their gate staff tell you that you have to reschedule your own missed flight online because they can't help you. I tried to reschedule my flight on my android device and instead, their website crashed and "cancelled" my missed flight. When I got to the counter, the agent argued with me for 5 minutes insisting that I intentionally cancelled my own flight (implying I had to buy another flight). She missed the point: the problem was that I could not buy another flight because their website is broken. I left to avoid more conflict with the "customer service" agent. I tried to redress my issue with their only other "customer service" chanel available: the contact form on their website. The response I got was more of the same: you cancelled your own flight, according to our website / computer records, therefore we won't help you. I was trying to explain the problem with their broken website that cost me hundreds of dollars by crashing / malfunctioning and resulting in a cancelled flight, but they only had deaf ears for this problem. Worst customer service I have ever experienced. I will never buy another Frontier flight again, because it is a risky, painful move that I will likely regret often.

What I expected, nickeled and dined and a frontier flight attendant loudly complained about her job and lack of communication as she headed to the gate on her cell phone. Not professional.

Severe turbulence. Captain never came on to reassure passengers after things settled down.

I’m not gonna fly Frontier Airlines because booking is not an option. No water or food is for high price, not equipped for health emergency incompetent crew for emergency services. Cheap airline shows it is cheaper in all service categories. Boarding is the best of all airlines!

We were delayed three times ,and that destroyed my plans, and reservations

Very bad! No good service delayed my second connection flight

Frontier is terrible. Paid for exit row, not given exit row, refused to refund fee.

2 hour delay due to late plane, wrong size plane causing overbooking, and people getting off and on the plane after boarding was completed.

Everything you need to know for your flight to Illinois

Cabin class types available on flights to Colorado

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

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