$99 Find Cheap Flights from Ontario to Illinois - Compare and Save

This is the cheapest one-way flight price found by a KAYAK user in the last 72 hours by searching for a flight from Ontario to Illinois departing on 8/12. Fares are subject to change and may not be available on all flights or dates of travel. Click the price to replicate the search for this deal.
1 adult
1 adult, Economy, 0 bags

KAYAK searches hundreds of travel sites at once for deals on flights to Illinois

 
These are the airlines KAYAK users have selected most often from within our search results in flight searches from Ontario to Illinois, as well as popular online travel agencies
These are the airlines KAYAK users have selected most often from within our search results in flight searches from Ontario to Illinois, as well as popular online travel agencies
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Cheap Flights from Ontario to Illinois

Cheapest round-trip prices found by our users on KAYAK in the last 72 hours
Chicago
Chicago2 stops$283
Moline
Moline1 stop$340
Peoria
Peoria1 stop$449
Bloomington
Bloomington1 stop$454
Springfield
Springfield2 stops$575
St. Louis
St. Louis1 stop$218
Paducah
Paducah1 stop$652
Chicago
Chicago2 stops$283
Moline
Moline1 stop$340
Peoria
Peoria1 stop$449
Bloomington
Bloomington1 stop$454
Springfield
Springfield2 stops$575
St. Louis
St. Louis1 stop$218
Paducah
Paducah1 stop$652

Book Cheap Ontario to Illinois Plane Tickets

 
Here are some of the best deals found on KAYAK recently from the most popular airlines for round-trip flights from Ontario to Illinois that are departing in the next months. While these flights were available on KAYAK in the last 72 hours, prices and availability are subject to change and deals may expire.
Discover the best prices for you by selecting your travel dates on KAYAK.

Recent round-trip flight deals from Ontario to Illinois

Tue, Jul 28 - Tue, Aug 4
Frontier Logo
10:49 am - 7:23 pm
ONT
-
STL
6h 34m
1 stop
Frontier Logo
8:08 pm - 10:04 am
STL
-
ONT
15h 56m
1 stop
$218Frontier
Wed, Aug 5 - Sun, Aug 9
Frontier Logo
6:00 am - 7:23 pm
ONT
-
STL
11h 23m
1 stop
Frontier Logo
7:10 pm - 8:03 am
STL
-
ONT
14h 53m
1 stop
$250Frontier
Wed, Sep 2 - Sat, Sep 5
United Airlines Logo
7:00 am - 1:10 pm
ONT
-
ORD
4h 10mnonstop
United Airlines Logo
8:06 pm - 10:35 pm
ORD
-
ONT
4h 29mnonstop
$283United Airlines
Thu, Sep 3 - Sat, Sep 5
Southwest Logo
12:50 pm - 11:20 pm
ONT
-
MDW
8h 30m
2 stops
Southwest Logo
6:00 pm - 8:10 pm
MDW
-
ONT
4h 10mnonstop
$283Southwest
Thu, Sep 10 - Sat, Sep 12
Southwest Logo
12:50 pm - 11:20 pm
ONT
-
MDW
8h 30m
2 stops
Southwest Logo
10:05 am - 4:00 pm
MDW
-
ONT
7h 55m
2 stops
$285Southwest
Tue, Sep 1 - Thu, Sep 10
Delta Logo
1:06 pm - 9:33 pm
ONT
-
ORD
6h 27m
1 stop
Delta Logo
1:50 pm - 8:07 pm
ORD
-
ONT
8h 17m
1 stop
$288Delta
Thu, Aug 13 - Thu, Aug 20
American Airlines Logo
12:59 pm - 11:30 pm
ONT
-
ORD
8h 31m
1 stop
American Airlines Logo
6:00 am - 1:31 pm
ORD
-
ONT
9h 31m
1 stop
$290American Airlines
Mon, Aug 31 - Sat, Sep 5
Delta Logo
11:56 am - 11:29 pm
ONT
-
ORD
9h 33m
1 stop
Delta Logo
6:00 am - 12:16 pm
ORD
-
ONT
8h 16m
2 stops
$293Delta
Tue, Jul 21 - Sat, Jul 25
United Airlines Logo
4:20 pm - 12:59 am
ONT
-
ORD
6h 39m
1 stop
United Airlines Logo
6:00 am - 12:47 pm
ORD
-
ONT
8h 47m
1 stop
$295United Airlines
Thu, Jul 30 - Tue, Aug 4
American Airlines Logo
11:59 pm - 10:39 am
ONT
-
MLI
8h 40m
1 stop
American Airlines Logo
4:45 pm - 11:59 pm
MLI
-
ONT
9h 14m
1 stop
$340American Airlines
Booking Insights

KAYAK's insights & trends for Ontario to Illinois flights

Get data-powered insights and trends into flights from Ontario to Illinois to help you find the cheapest flights, the best time to fly and much more.

How much is a round-trip flight from Ontario to Illinois?

This analysis is based on the cheapest round-trip price found on KAYAK in the last 12 months by searching for a flight from Ontario to Illinois departing in September.

What is the cheapest Ontario to Illinois flight route?

Data is based on round-trip flight searches on KAYAK over the past month.

The cheapest ticket to Illinois from Ontario found in the last 5 days was to Chicago, at $297 round-trip. The most popular route is from Ontario (ONT) to Chicago O'Hare Intl Airport (ORD), and the cheapest round-trip airline ticket found on this route in the last 5 days was $297.

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

The average price for all round-trip flights from Ontario to Illinois depending on the time of departure, clicked by users on KAYAK in the last 2 weeks.

The cheapest time of day to fly to Illinois is generally in the morning, when round-trip flights cost $483 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 $526.

Can I save money by flying with a layover from Ontario to Illinois?

The average round-trip price for all non-stop flights, flights with one layover, and flights with two layovers for the route found by users searching on KAYAK in the last 2 weeks.

No, with an average price for the route of $460, prices are generally cheapest when you fly direct.

What is the cheapest month to fly from Ontario to Illinois?

To calculate monthly average prices, KAYAK takes all prices for each month over the last year for round-trip flights from Ontario to Illinois, removes the top 0.1% to account for outliers, and then takes the median of all values for each month.

The cheapest month for flights from Ontario to Illinois is September, when tickets cost $102 (return) on average. On the other hand, the most expensive months are March and May, when the average cost of round-trip tickets is $186 and $186 respectively.

What’s the cheapest day of the week to fly from Ontario to Illinois?

The average price of all round-trip flights from Ontario to Illinois clicked on KAYAK for each day over the last 12 months.

If your flying dates are flexible, you should consider flying to Illinois on a Wednesday, as we generally find the cheapest rates on that day for this route. On the other hand, Sunday is the most expensive day to fly from Ontario to Illinois. For your return ticket, we recommend flying on a Wednesday and avoiding Sundays for the best deals.

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

To calculate weekly average prices, KAYAK takes all prices for each week before departure over the last year for round-trip flights from Ontario to Illinois, removes the top 0.1% to account for outliers, and then takes the average of all the values for each week.

To get a below average price on the flight from Ontario to Illinois, you should book around 4 weeks before departure, which saves you about 38% compared to booking last minute. For the absolute cheapest price, our data suggests you should book 9 weeks before departure.

Good to know

Low seasonJanuary
Cheapest flight$99
Best time to beat the crowds with an average 6% drop in price.
Most popular time to fly with an average 16% increase in price.
Flight from Ontario to Chicago O'Hare Airport

FAQs - booking Illinois flights

  • How does KAYAK find such low prices on flights from Ontario 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 Ontario to Illinois.

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

    KAYAK’s flight Price Forecast tool uses historical data to determine whether the price for a flight from Ontario 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 Ontario 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 Ontario 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 Ontario 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 Ontario to Illinois up to 3 days before/after your preferred dates. You can then pick the flights that suit you best.

Top tips for finding cheap flights to Illinois

  • Looking for a cheap flight? 25% of our users found tickets from Ontario to the following destinations at these prices or less: Chicago $263 one-way - $427 round-trip; Chicago $249 one-way - $415 round-trip

Reviews of the top 5 airlines serving from Ontario to Illinois

 
See real verified KAYAK customer reviews for airlines flying from Ontario to Illinois. Airline scores are aggregated from all reviews left by passengers on KAYAK after flying with an airline. KAYAK doesn’t show reviews that are older than 5 years. Learn how KAYAK collects reviews.
Need help choosing which airline to fly with from Ontario 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.
7.9
SouthwestOverall score based on 4246 reviews
8.6Crew
7.0Food
8.1Boarding
7.5Entertainment
8.0Comfort
Airline reviews

Flight was delayed, full flight and I had to change gates. Southwest flights are always late later in the day.

4.0 OkaySteven, Jun 2026
ONT - LAS
Read more Southwest reviews

Flight was delayed, full flight and I had to change gates. Southwest flights are always late later in the day.

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.

Flight was ok. Boarding wasn’t fun. Flights were delayed by 12 minutes on each leg.

Wifi didn’t work, no service, seats are hard as rocks

I liked receiving attention from aged and well experienced flight attendants. I disliked the non-gluten-free snack but I brought my own so I was OK.

It was as good as it could be. Flying is not a pleasant experience these days.

There was an unruly family behind us that made the short flight miserable!!! The cabin crew did nothing to contain it.

Flight delay was frustrating, also you cannot checkin online without delta app, web browser check-in throw errors

Got on the plane and sat there for an hour before departure.

Very large passenger too space from my own seat. Arm board couldn’t be lowered because of his size. It wads very uncomfortable trip, as the flight was full couldn’t move anywhere having back pain because of the position in which I was the entire flight.

It was a great flight and the stewards and stewardess were all kind and accommodating!! The seats were comfortable and entertainment screen excellent!

737-800 in first class was pretty dumpy. Seat had an uncomfortable angle, storage under the seat was blocked so even my very modest backpack didn't fit, power outlet was flaky. Weird tiny seat pockets that couldn't hold a gallon ziploc bag, emesis bag missing, etc. etc. No in-flight service due to turbulence. Crew was excellent, boarding was smooth despite a full flight.

The flight was overbooked and the staff at the gate started calling for volunteers to drop out and offering incentives. That delayed the flight

There was no wifi even after my husband paid for wifi it wasn’t working. The plane looked and felt old.

Update the cabin with tv screens or at least music sources.

Seat pitch is horrible especially on the 15 hour flight. Gate crew at SFO was Outstanding. The flight crew was also great.

Crew was great (professional, attentive, prompt). Snacks for 4 hrs flight is deplorable.

It was a pretty standard flight... until the almost hour and a half spent on the taxi way. I get that the weather has been poor but the delay had nothing to do with the weather and more to do with a plane with several issues tying up the gate. I get that that happens from time to time but this has been EVERY flight I've been on for the past 5 years and I fly 3 to 5 times a year. This isn't just United... it's American, it's Delta. It's an issue with the entire industry. I work for UPS and packages on a cargo plane get better service than people do these days. Anymore I HATE flying.

While the staff was pleasant and helpful, the following observations are for your awareness. There was some delay on the tarmac on take off and landing. The paid lunch/food offerings were limited. Entertainment was only available on WiFi at a cost.

The first flight was better in terms of the aircraft.

As usual, United scheduling is completely misleading. A 54-minute layover at O’Hare is too short to make a lot of connections, especially since the flight landed “on time” but had to wait on the taxiway 15 minutes for a gate to open up. Then it takes another 10 minutes to exit the plane before one can run to another concourse to catch a connecting flight.

when you can say you don't remember being at any point upset during a flight, the airline is winning .

I had a great flight. Everything went smoothly and the flight arrived early.

United WiFi is consistently unusable (it can take 10 mins to load a single web page). If you need Wifi to do work, be prepared to lose half a day of productivity.

The Palm Springs to Chicago O’Hare was on Time and Palm Springs airport is easier navigate. As our connection was only an approximately 50 minutes, we asked staff for insights for the Chicago airport in terms of transferring into the other terminal from which our flight left, and they were unhelpful. However, the United App was very helpful in terms of notifications and even providing directions. The Chicago to Detroit flight was significantly delayed which we all know does happen. However, there were very few updates or notifications as to why this was happening when we would actually arrive. It took nearly 30 minutes for bags to make it to baggage claim. We arrived nearly 1 hour late on a 40 minute flight.

The flight from LA to Chicago was smooth and service was very good overall.

Ontario airport boarding was very easy to park and access, is clean and TSA took 10 minutes total. Check-in was a breeze and cruise was very nice.

Good flight, seated and had a water within 5 minutes. Crew was hospitable.

The chicken wrap was tiny ($13 for what looked like a 1/3 of a normal wrap?) and disgusting.

We flew in first class. The crew did not offer drinks before the flight took off, but they treated us well during the flight. The food was excellent. There was actually too much food served, but it was nice to have all the options.

The flight was on time and arrived early. The crew were friendly and helpful.

Was not able to watch most shows on the entertainment site. They would not load

The chair cushions may need an upgrade. I have been noticing they are so worn out, thin so you’d sit in a dip 😄. Other than that, all was an enjoyable trip. Thanks AA!

VERY disappointed at the agent checking in my luggage. I know that the weight limit is 23 kg, a little over 50 pounds (50.71 pounds). Yet the agent kept repeating "50 pounds". So I said, the limit is 23 kg, and she had the audacity to say 'no, it is 22 kg!" Imagine my surprise. Was she ignorant or was she poorly trained? Not sure. The boarding process was pretty good. The speakers were loud enough so I still could hear them despite inconsiderate passengers continuing to speak while the announcements were going on. During the flight, the teenage girl sitting behind me kept pressing her feet to the back of my chair. I turned around several times, yet she did not get the hint. I did not make a fuss since I sense I had a bad streak that night with AA, so I just did the best I can to lean forward and not let that bother me.

It was wonderful upgrading to first. Plane was so cold thou. Crew was great. Wish there was a food option in first for such a long flight. Doesnt matter the time of day. Chintzy.

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

The takeoff was the smoothest I've ever experienced on any airline and this is the first time I've flown on frontier so this was an extremely pleasant surprise!

A lady asked to stop the flight after the tunnel pulled away and we began to depart a flight that was already hours late. The attendance respectfully stopped the the plane and had the tunnel return. After the tunnel returned the passenger claimed to have changed her mind . The tunnel was then put in reverse and the passenger remained on the plane .. They should have sent the sick passenger off the plane like initially replaced. They existed a couple off the plane prior to that situation.. So.. all and all.. it was a long and flight.. .

We understand and comply with Frontier’s bag sizes. We’ve had some problems in past while having to await other passengers who do not understand the baggage restrictions or have not prepaid and that is usually our biggest concern (others delaying us) with flying Frontier. Flying OUT of ONT, however, has always been a great experience. I’ve also noted even on delayed Frontier flights very knowledgeable pilots who manage expectations well.

Long lines, rude staff, everything that's offered you have to pay for.

The last time I flew Frontier was in the 1960s when it was a “real” airline. We flew this time because of the price & schedule. As the saying goes, you get what you pay for.

I appreciated the upgrade to free cary-on bag and seat selection at no charge

Flight was delayed on the runway for 40 minutes the crew did not even offer even water to passengers to compensate for the flight delayed. The flight was delayed due to aircraft mechanical issues. Worst customer service ever

This isna terribly run airlines. If you're one minute late, they will deny your ticket. Don't waste your time or money

Flight was delayed for more than 3 hours, crew at ONT airport was rude, and when we got to DFW the airplane had an issue landing, we had to be taxied to the terminal, and the luggage was hold until the next day.

Everything you need to know for your flight from Ontario to Illinois

Information on your arrival and departure airports