$43 Find Cheap Flights from Colorado to Illinois - Compare and Save

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Low season

January

Cheapest flight

$43
Best time to beat the crowds with an average 7% drop in price.
Most popular time to fly with an average 3% increase in price.
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 
JoanneFlew with United Airlines-Jun 2026
The runway to gate took a bit of time. So if you have a short layover pay for a seat up front .
AdamFlew with Southwest-Oct 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 Airlines-Jan 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 (216 flights per week), Air Canada (143 flights per week), and American Airlines (112 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 91% 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 Greater Peoria Airport (PIA), with an average flight price of $149.

  • What is the cheapest day to fly to Illinois?

    Based on KAYAK data, the cheapest day to fly to Illinois is Friday where round-trip tickets can be as cheap as $330. On the other hand, the most expensive day to fly is Sunday, where round-trip prices are $547 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 $259 on average. Morning departures are around 11% more expensive 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 $548.

  • What is the cheapest flight to Illinois?

    The cheapest ticket to Illinois from Colorado found in the last 5 days was to Peoria, at $101 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 5 days was $150.

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

    The cheapest month for flights from Colorado to Illinois is November, when tickets cost $158 (return) on average. On the other hand, the most expensive months are January and February, when the average cost of round-trip tickets is $227 and $214 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 44% compared to booking last minute. For the absolute cheapest price, our data suggests you should book 10 weeks before departure.

  • How many cities have direct flights to Illinois?

    From Colorado, there are direct flights to Illinois from 5 cities. The city with the most direct flights is Denver, with 867 direct flights each week.

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

    There are around 147 direct flights from within Colorado to Illinois every day. Most flights (56%) depart in the morning.

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

    Each week there are around 1,028 direct flights from within Colorado to Illinois. The most common day for departures is Sunday, with 17% of flights taking off on this day.

  • How long is the flight to Illinois?

    An average nonstop flight from Colorado to Illinois takes 5h 55m, covering a distance of 927 miles. The shortest route is Denver (DEN) to St. Louis (STL) with an average flight time of 1h 55m.

  • 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 1,028 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 (85% of total searches to Illinois). The next most popular destinations are St. Louis (13%) and Peoria (2%). Searches for flights to Bloomington (0%) and to Champaign (0%) 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 4195 reviews
7.0Food
7.5Entertainment
8.6Crew
8.1Boarding
8.0Comfort
Airline reviews

Flight was delayed over 3 hours. Planes were dirty. Staff indifferent. And they serve vegan pretzels as snacks.

2.0 MediocreMatthew, Jun 2026
Read more Southwest reviews

Flight was delayed over 3 hours. Planes were dirty. Staff indifferent. And they serve vegan pretzels as snacks.

The flight was smooth. The Southwest experience has degraded overall, but this one was okay.

The checking experience in Orlando was terrible, almost missed the flight. Too many travelers and Southwest completely understaffed.

no service at all due to turbulence. they should've at least given us snacks, there were only 10 people on the entire flight.

For the first time in a long time, the Wi-Fi actually worked the entire flight! The flight crew was amazing as usual.

Great flight. I didn't get a drink because I was asleep whole on the flight.

Love them will get a Southwest card to track my points and keep flying with them. My family and I were pleased with the services.

WiFi was not working and didn’t have a beverage service

All good except once again bags took an hour at Midway Airport Happens all the time. Ridiculous

Delay after delay after delay. Very disappointing I am about ready to give up on Southwest. One of the crewmembers sat and played games on her phone for the entire trip from Chicago to Baltimore. Unbelievable, very unprofessional, and very disappointing.

Crew was great. Seats are cramped and uncomfortable and I’m a small person.

Awful. Delay after delay. And then again on the tarmac.

Very easy ! Use the kiosk and bag drop and right to security within 10 min

O’hsre taxi and deboarding took 40 minutes. Needed 20 minutes extra time between connecting flights to avoid running through terminal.

Every staff member was professional, friendly and courteous. The pizza twist was ok. It was warm but too much dough.

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.

Overall poor for me I paid extra for seats with leg room and my regional flights exit row seats have less leg room then the others that's money that could have been saved and on my final flight home the flights air was not operating it was unbearably hot in the cabin I will be contacting United and filing a DOT complaint

Flight was delayed by over an hour and gate checked bags took 15 minutes to be delivered to the jet bridge.

We have taken this flight before and it is a tight connection and they were late out of denver and did not wait for us. The plane was there and the departure time had not passed but would not let us on. Next flight is very late and a connection through Newark - a big mess. Sooooo appreciate them holding the plane so we could catch the connection.

Upgrade planes to have larger overhead bins, especially on this popular route and first class. Easy flight to Chicago, good service in first class. Can't wait for seatback entertainment to be brought back. I like the free wifi and messaging with T-Mobile. Although, the tray tables are not big enough to work even on a small laptop - so why is it called "business" class?

It was a dismal experience. The flight was delayed for 4 hours, and we spent hours in the plane, without air, during the summer. We were not provided with water, and the medical assistance was inadequate when it arose.

The landing the pilot was very smooth. The flight attendant was kind of rude.The boarding the plane in punta Gorda was not great made us wait out in the heat 😞

My exit seat was very comfortable Coffee was to be purchased but sodas free 😏

It was poor a four hour delay and no explanation for the delay. What’s a 35 dollars going to do. It also made me miss my car rental,

It was on time. Flight was comfortable. Staff was nice. It was the way a flight should always be.

The price was the only good thing about this flight. It was scary during takeoff when the plane tilted side to side. It made me feel very nervous as I have never had a take-off that unsmooth. There was no on-flight movie or music options and the only complimentary option was water. Other airlines offer trail mix or a caramel cookie and pop options as complimentary. This flight was a 2.5 hour flight. I understand for shorter flights not having options, but a flight 2 hours or longer should offer more complimentary options and in flight entertainment. Also the seats did not recline and for a longer flight reclining seats are a must for comfort.

It was cold on the flight. The crew was very pleasant. I didn't order any food. We were delayed due to Captain waiting on maintenance log. He kept us informed though. The flight itself was smooth. I would definitely fly with Allegiant again!

My 90 year old father flew with me. He needed wheel chair assistance and is nearly deaf. The staff was amazing with him.

The flight was delayed 6 hours and we were only offered an $8 food credit. My husband stood in line to get the credit for 45 minutes and when he got close to the end of the line the computers went down.

Be just a little friendlier, instead of just doing their job and speaking because it’s their job. At least act they want to speak.

Our flight from Chicago to Des Moines was the problem flight due to a dismissive flight attendant. His conduct was unnecessary and unprofessional.. I will avoid using Americam Airlines again because of the situation. Very disappointing.

Mostly excellent. However, many too many gate changes. Connecting flight at ORD changed gate 6 times.

Mechanical issues and delays. I get it but bad experience. Turned my 3 hour airport experience into a 9 hours

The baggage process at the gate was terrible. Stay was not friendly at all

Flight was delayed because of mechanical. Could not get landing space which caused me to miss my connection. Messy and not organized.

We landed slightly early but then sat in holding area waiting for our gate to clear out for about an hour, so technically we arrived one hour late at the gate at ORD. The airport may be partially responsible here, but regardless of who is responsible, it was a bad experience to be so close yet unable to get off the plane.

Delays and cancellations. Mechanics weren’t on site. Replacement plane took hours to arrive although it should have arrived within 90 minutes. Flight back was cancelled. Ended up driving over 12 hours and wasting 3 days between everything.

The flight attendants were extremely sourly and borderline rude. I did not feel appreciated as an AA customer once.

It was great. It was just a commuter so I splurged on first class and it was wonderful. Wish all seats were this spacious. Enjoyed it and will do it again.

Deicing in Denver took forever and I almost missed my connection. De-ice faster! Not Americans fault.

Flight was scheduled at 9:40pm. Got delayed to 10 am, the next day. crazy

The bag check, flight check-in, and onboard experience convinced my wife and me that we will actively go out of our way to avoid flying Frontier Airlines in the future. At bag check, we were informed that check-in could only be completed via the Frontier mobile app. Unfortunately, the app was extremely frustrating—sending us through repetitive, confusing loops that repeatedly forced us to decline add-on services with nearly every click. While most airline apps upsell, this one felt intentionally exhausting. As the process dragged on, we became genuinely concerned that my phone battery would die before check-in could be completed. We approached the bag check staff—who were standing together talking—and explained both our frustration and our predicament. They laughed. Later, my wife described the interaction as “gaslighting,” which felt accurate. We were then informed it would cost $25 per person simply to have our boarding passes printed. From that point forward, the tone of the experience was consistently hostile. The bag check employees were condescending and combative, behaving more like bullies than customer service staff. Unfortunately, that same attitude continued onboard. One flight attendant argued with me when I attempted to stow my backpack in the overhead bin. I explained that we had each paid $75 to check our bags specifically so we would not need to use carry-on space and could have adequate legroom. She demanded to see my ticket, pointed out that it said “no carry-on”—which I acknowledged—and I reiterated that this was precisely why we paid to check our bags. Her response was, “I don’t make the rules.” She then walked away, but not before asking if I “truly wanted to fly back to Chicago today?”—an unnecessary and unmistakable threat. It is also worth noting that despite booking our tickets together in the same transaction, we were not seated together. Upon our return to Chicago—where we could once again sit together—we compared onboard experiences. We both remarked on how unhappy the flight attendants appeared and how each of us was separately asked whether we would like to purchase a beverage. We declined. At no point was water mentioned as an option, leaving us with the clear impression that even water came at a cost—or that complimentary water, if available at all, was deliberately left unmentioned. Overall, the experience was shocking and deeply disappointing, but it was also a profound learning experience—one we will not forget and will not repeat. -Steve

Good for a budget airline! It was easy to get on, staff was really nice. Can’t say anything about the food or entertainment because it wasn’t available, which is fine.

This company socks. It's fraud. They canceled our flight yesterday, and today we were late because of a really long line at the check in bag. At the rebook station, there was ton of people. The workers were all rude. I am gonna make a report to FTC.

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.

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

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

The crew was delayed because they came on another flight that was delayed due to weather 10pm flight left at 1.30 am The airline made no effort to align alternate crew

The flight itself was ok and the pilot was very communicative. However, our flight was delayed for almost 3 hours, the gate was changed 3 times and there was no communication as we were waiting. The flight staff was overall a little crabby...I understand as they probably had a long day but we all did.

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