$35 Find Cheap Flights from Illinois to Colorado

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Low seasonNovember
Cheapest flight$35
Best time to beat the crowds with an average 6% drop in price.
Most popular time to fly with an average 10% 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 airlines fly most frequently to Colorado?

    Illinois and Colorado are connected by different airlines. The airlines that fly that route the most regularly are United Airlines (113 flights per week), Air Canada (82 flights per week), and Southwest (44 flights per week).

  • How many airports are there in Colorado?

    There are 12 airports in Colorado. The busiest airport is Denver Airport (DEN), with 91% of all flights arriving there.

  • 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 $211.

  • What is the cheapest day to fly to Colorado?

    Based on KAYAK data, the cheapest day to fly to Colorado is Saturday where round-trip tickets can be as cheap as $238. On the other hand, the most expensive day to fly is Monday, where round-trip prices are $298 on average.

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

    The cheapest time of day to fly to Colorado is generally at night, when round-trip flights cost $244 on average. Morning departures are around 13% cheaper 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 $298.

  • What is the cheapest flight to Colorado?

    The cheapest ticket to Colorado from Illinois found in the last 72 hours was to Denver, at $118 round-trip. The most popular route is Chicago Midway Airport (MDW) to Denver (DEN) and the cheapest round-trip airline ticket found on this route in the last 72 hours was $118.

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

    The cheapest month for flights from Illinois to Colorado is September, when tickets cost $309 (return) on average. On the other hand, the most expensive months are July and December, when the average cost of round-trip tickets is $594 and $539 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 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 9 weeks before departure.

  • How many cities have direct flights to Colorado?

    From Illinois, there are direct flights to Colorado from 3 cities. The city with the most direct flights is Chicago, with 493 direct flights each week.

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

    There are around 73 direct flights from within Illinois to Colorado every day. Most flights (33%) depart in the morning.

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

    Each week there are around 507 direct flights from within Illinois to Colorado. The most common day for departures is Friday, with 16% of flights taking off on this day.

  • How long is the flight to Colorado?

    An average nonstop flight from Illinois to Colorado takes 6h 12m, covering a distance of 931 miles. The shortest route is St. Louis (STL) to Denver (DEN) with an average flight time of 2h 15m.

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

    There are not any long-haul (6-12 hour flight duration) or medium-haul (3-6 hour flight duration) flights to Colorado. Instead, there are 507 short-haul flights (up to 3 hour flight duration), with the most arriving from Chicago.

  • 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 (5%) and Montrose (1%). Searches for flights to Aspen (1%), to Grand Junction (1%) and to Durango (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 4331 reviews
8.1Boarding
7.5Entertainment
8.6Crew
7.0Food
8.0Comfort
Airline reviews

Southwest is kind of a slum airline. It’s gotten more expensive over the years for less and less service. I am a Southwest Chase Visa card holder and was forced to choose a seat in the 26th row in the middle seat. However my wife who is a rewards member but doesn’t hold a card or anything else, gets randomly assigned a normally paid seat in row 6! How does that work?

4.0 OkayDavid, Apr 2026
COS - DAL
Read more Southwest reviews

Southwest is kind of a slum airline. It’s gotten more expensive over the years for less and less service. I am a Southwest Chase Visa card holder and was forced to choose a seat in the 26th row in the middle seat. However my wife who is a rewards member but doesn’t hold a card or anything else, gets randomly assigned a normally paid seat in row 6! How does that work?

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

The seat was not comfortable. 1D. My back was sore all night and the next day.

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

Great flight from Seattle to Phoenix and to Chicago-Midway from Phoenix

I flew twice this week on Southwest, was delayed over 2 hours both ways. From Pittsburgh to Chicago it was due to weather but the gate agents, pilot etc were great at updating everyone. Today from Midway to Pittsburgh the plane had come from an international location, kept getting delayed, no information was given until we were delayed for the third time. It was ridiculous, whoever scheduled that plane to fly to Pittsburgh after didn’t consider a lot of things.

I appreciate the staff who allowed me to board though I arrived a little late! Regarding the assigned seating, I had booked my flight before this change and wasn't aware of the change at the time, and so I didn't select a seat at booking as I didn't realize it was relevant. Better communication about the change would have been helpful for preparing.

The staff was very friendly, professional, and courteous. The overall flight was a great experience.

Plane crashed into a bus or some other vehicle on the ground while pulling out of the gate. No injuries, but wing tip was damaged and returned to gate for “maintenance issues” and we departed 5 hours later because the plane went out of service and new plane was flown in from a nearby airport, Midway.

All was good. I just had a hard time getting connected to the WiFi/internet during the flight

The flight crew on this leg of my trip was very friendly and pleasant. Every one of them was humorous, as well as helpful and accommodating. This group was BY FAR the best crew I’ve flown with. They deserve kudos.

The entertainment options on the seat back video boards were nice.

The boarding process was straightforward. One pertinent observation regarding all boarding procedures is that if an individual requires assistance or possesses a special status and is part of preboarding, it is advisable to limit the number of passengers who can preboard with them, rather than the entire, sometimes large, companion groups. The seats are uncomfortable, and the entertainment options are significantly inferior compared to other airlines. During the snack service, I requested an additional bag of snacks, but my request was denied. Initially, the flight attendant agreed to my request.becoming a strange accurate moment. The flight duration was four hours.

I had a cancelled flight because of technical issues going to my destination, and a delayed flight coming home. All told it wasn’t a total bust.

During landing. 2 crew members passed 3 times by my lane and didn't notice that people in front of us had their site to the furthermore reclined... That was uncomfortable and could have been dangerous.

Seats are uncomfortable. This has been a trend in the industry for decades. Trying to fit more seats on each plane to increase profits at the expense of the passenger.

It’s always a great time flying with united airlines.

We got delayed three hours and nobody thought to have the bathroom fixed while we were sitting waiting to board? took a full hour to have maintenance come and check it off. Had to shut the bathroom down twice so that the pilots could go to the bathroom. Everyone missed their connections.

Women boarding passengers at the gate was absolutely rude and disrespectful of passengers. The flight attendant was absolutely delightful! Smiling and connected with the passengers. So happy. The seats are cramped and uncomfortable but I guess that’s just the way it is Communication regarding flight was excellent

As great a red-eye flight as red-eye flights can be.

No food is available without purchasing it and there is no in-flight entertainment. Both of these are OK because we got an inexpensive flight from Allegiant and, otherwise, our experience was excellent.

just had water and there was plenty of leg & seat room. But then i don't weight 220#s!!

Not totally their fault- screaming kids that had zero parent intervention.

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!

I had a fantastic experience with Allegiant. I had wheelchair assistance and they helped me find my luggage and brought me to my car. Even loaded my luggage. Wonderful service!! Thank you Allegiant!

Superb. Staff great. Great flight. As with other airlines, seating too tight and restrictive.

There is not one likable thing about this airline. It’s starts with the deceptive pricing and continues through the whole flight. The worst staff I’ve ever experienced way over priced bags absolutely no food or drink (unacceptable and you should be embarrassed) the seats are cramped and uncomfortable there is no entertainment there is nothing about this trash airline that constitutes any amount of money. It’s worse than spirit and way more expensive it is disgraceful. Do not travel with Allegiant I repeat do not bother no matter what they say the price is it is never ever going to be the right choice I’m mind blown at how awful the entire experience was I’m embarrassed that I chose so poorly I cannot reiterate enough how beyond horrible this company and its staff are, not one person on this flight or at the airport is qualified to sweep up trash on a city sidewalk they should certainly never be given any job that requires a brain or manners or communication with human beings, what a disgrace to the human race. Your criminal chiselers and should be put out to pasture

Great flight. Friendly staff. Free snacks and drinks would be nice. I would love fewer taxes and fees added on.

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

It was fine. Nobody was outstandingly friendly but no one was rude and everything was smooth . The captain thanked us for flying but no one greeted me as I walked on the plane or as I exited which is the least they could do lol

Original flight was on time, then late, then changed gates...4 times. Once our newest plane came in, it was fine.

Everything was delayed and the staff sent me to the wrong gate, causing me to miss one of my flights. I arrived at my destination 6 hours later than I was supposed to.

I almost missed my flight and they helped me out enormously

Delays experienced in boarding/take off due to incoming plane delayed. However, the boarding time/depart time in the app was significantly delayed in providing these updates. Usually not updated until an hour after we should have already boarded. Poorly managed.

Moved to earlier flight which unexpectedly had maintenance issues initially indicated as quick fix to ultimately plane changes. Moved back to original flight, also delayed. In all cases customer updates and communication very unclear, no updates on drivers for delays.

On the return flight, arriving in Denver we sat on the tarmac in Denver for over 20 minutes.

Typical AA - late by 90+ mn. Gate changed twice... Changed the departure time 6 times No explanation, no communication on reasons for delay I travel with AA twice a year... and it is consistently very poor.. I will continue to use AA only when i have to.

The gate got changed several times and the flight was delayed over an hour. Awful experience

American continues to decline in their customer service and its beyond disappointing.

It was an older plane. First Class was not especially roomy or comfortable. It was a short flight so there were no meal but they did offer mixed nuts which used to be normal but now is rare. Crew member was very polite and professional.

It was an early flight and most people napped/slept and the crew let us which was nice.

More inflight connection. And leg space is horrible. And the paying for baggage I'd ridiculous!!!

Flight was canceled. Most upsetting was message from Kayak, stating that the flight was canceled and click with Kayak for details regarding rebook, refund details. THERE'S NO INFORMATION PROVIDED BY KAYAK EXCEPT THAT FLIGHT IS CANCELED. AND NOW THIS SURVEY TO FIND OUT HOW WAS THE FLIGHT !!!!!!!

It was costly and difficult to check in. $85 to take a small suitcase with me, carry on or checked and $75 on the return trip, Plus $25 if I didn't check my self in check in $25, because I couldn't do it on the kiosk. Small very uncomfortable seats, waited on the runway for near an hour each way. It was my worst flight to date.

Due to weather, my flight was delayed, further delayed, then canceled. I eventually got through to a support person who helped me find a different route out of MSP, but to get to DIA, they didn't want to, but eventually did help with the connection ticket purchase. But even this replacement flight was delayed time and time again, and I would have missed my connecting flights and I didn't want to get stuck in a layover city, so after 12 hours at the airport with two young boys who were very tired, we just cancelled our plans and spent the week at home, instead of Nana's.

Better than expected. Staff were friendly and nice on both flights.

I knew going into this that Frontier, being a low cost carrier, would be pretty bare bones and charge for most extras but this was made up for by the fact that the airplane was a reasonably new Airbus, every employee was great and best of all, Everett Washington is an amazing airport - thanks Frontier for flying there!!!

Just know that everything, and I mean everything is “ala cart”. 60$ just to put something in the overhead bin. I will never fly Frontier again nor do I recommend them to anyone else.

Seats were new and comfortable. Staff was fine. Missed my connection due to weather -which wasn’t their fault- but got no help at all. Gate staff sent me to customer service, which was and stayed unstaffed. Sign with QR code directed me to call or chat. Chat was useless. Call was returned after an hour. No itinerary offered by Frontier could get me home in less than 30 hours. Rebooked with another airline and got a partial refund that came to about 10 percent of what I paid to get home.

The experience was good. No frills but I got there safe and sound and on time.

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.