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Ontario

$107+ Cheap flights from Illinois to Ontario (ONT)

This is the cheapest one-way flight price found by a Cheapflights user in the last 72 hours by searching for a flight departing on 7/28. Fares are subject to change and may not be available on all flights or dates of travel.
ORD — ONT
Jul 7 — Jul 141
Tue 7/7
Tue 7/14
1 adult, Economy
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Cheap flight deals from Illinois to Ontario

Cheapest flights from Illinois to Ontario
Explore the most affordable flight options available from Illinois to Ontario. Find the lowest fares from popular airlines and budget airlines, with prices last updated on June 7, 2026.

This Kiwi.com deal was found by Cheapflights users on 6/3. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 8/49:34 pm
ORD
-
ONT
1 stop13h 03m
Frontier
Tue 8/1810:50 am
ONT
-
ORD
1 stop8h 03m
Frontier
Deal found 6/3$171
This Kiwi.com deal was found by Cheapflights users on 6/3. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 7/213:41 pm
STL
-
ONT
1 stop18h 56m
Frontier
Wed 7/296:00 am
ONT
-
STL
1 stop11h 23m
Frontier
Deal found 6/3$191
This Kiwi.com deal was found by Cheapflights users on 6/3. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 7/277:15 am
ORD
-
ONT
1 stop26h 48m
Frontier
Tue 8/43:40 pm
ONT
-
ORD
1 stop11h 57m
Frontier
Deal found 6/3$195
This Kiwi.com deal was found by Cheapflights users on 6/3. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 7/79:34 pm
ORD
-
ONT
1 stop13h 03m
Frontier
Tue 7/216:00 am
ONT
-
ORD
1 stop12h 52m
Frontier
Deal found 6/3$205
This Kiwi.com deal was found by Cheapflights users on 6/2. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 6/239:48 pm
ORD
-
ONT
1 stop14h 17m
Frontier
Tue 6/303:34 pm
ONT
-
ORD
1 stop11h 33m
Frontier
Deal found 6/2$221
This Gotogate deal was found by Cheapflights users on 6/2. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Gotogate is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 8/85:46 pm
ORD
-
ONT
1 stop15h 46m
Frontier
Wed 8/123:40 pm
ONT
-
ORD
1 stop11h 57m
Frontier
Deal found 6/2$226
This Booking.com deal was found by Cheapflights users on 6/2. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Booking.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 8/59:57 pm
ORD
-
ONT
1 stop14h 07m
Frontier
Wed 8/121:38 pm
ONT
-
ORD
1 stop13h 59m
Frontier
Deal found 6/2$228
This Kiwi.com deal was found by Cheapflights users on 6/3. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 7/299:57 pm
ORD
-
ONT
1 stop14h 07m
Frontier
Wed 8/1910:50 am
ONT
-
ORD
1 stop8h 03m
Frontier
Deal found 6/3$234
This United Airlines deal was found by Cheapflights users on 6/3. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 7/298:18 pm
ORD
-
ONT
Nonstop4h 33m
United Airlines
Wed 8/197:00 am
ONT
-
ORD
Nonstop4h 10m
United Airlines
Deal found 6/3$239
This Expedia deal was found by Cheapflights users on 6/5. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Expedia is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 7/89:57 pm
ORD
-
ONT
1 stop14h 07m
Frontier
Tue 7/1410:49 am
ONT
-
ORD
1 stop8h 03m
Frontier
Deal found 6/5$240
This Frontier deal was found by Cheapflights users on 6/3. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 8/69:27 pm
MDW
-
ONT
1 stop13h 10m
Frontier
Tue 8/118:17 am
ONT
-
MDW
1 stop6h 34m
Frontier
Deal found 6/3$240
This Kiwi.com deal was found by Cheapflights users on 6/2. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 10/2411:06 am
ORD
-
ONT
1 stop14h 49m
Frontier
Tue 10/272:35 pm
ONT
-
ORD
1 stop17h 26m
Frontier
Deal found 6/2$241

Find flight deals from Illinois to Ontario

Keep the following information in mind while searching for Illinois to Ontario flight deals. Data was last updated June 7, 2026.

Most accurate provider

FlightHub
3 stars

Most trusted provider

FlightHub
3 stars

Round-trip from

$171
(Kiwi.com)

One-way from

$107
(Kiwi.com)

Popular in

December

Cheapest in

September

Average price

$317

Good round-trip deal

$284 or less

Good one-way deal

$218 or less
Provider with most accurate pricing for Chicago (CHI)-Los Angeles flight deals.
Search Deals
Provider most trusted by Cheapflights users for Chicago (CHI)-Los Angeles flights.
Search Deals
From Illinois to Ontario
Search Deals
One-way flight from Illinois to Ontario
Search Deals
Highest demand for flights based on searches. 10% potential increase in price ($35 potential increase over avg. RT price).
Search Deals
Cheapest flight prices on average. 2% potential price decrease ($7 potential savings vs. average RT price).
Search Deals
Average for round-trip flights in June 2026
Search Deals
Price to beat on a round-trip flight from Illinois to Ontario.
Search Deals
Price to beat on a one-way flight from Illinois to Ontario.
Search Deals

Cheapflights Fare Finder

 
Customize your flight search to find flights from Illinois to Ontario that fit within your specific budget. Explore options based on user searches and filter the results based on your desired price range. Find flights that match your budget for a cost-effective journey. Over the last 7 days, Cheapflights users made 2,558,603 searches. Data last updated June 7, 2026.
Use the filters below to find and compare flights from Illinois to Ontario that are best for you.

Fly from

Fly to

Route

Depart

Return

Price

Cheapest round-trip

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Tue 9/1

8:08 pm-11:49 pm

1 stop5h 41m

Ontario

Wed 9/2

6:00 am-7:23 pm

1 stop11h 23m

$264

MolineOntario

MLI - ONT

MLIONT

Moline Quad-City

Wed 7/1

4:46 pm-11:59 pm

1 stop9h 13m

Ontario

Tue 7/7

2:15 pm-11:30 pm

1 stop7h 15m

$331

MolineOntario

MLI - ONT

MLIONT

Moline Quad-City

Sat 7/4

7:20 am-1:20 pm

1 stop8h 00m

Ontario

Fri 7/10

11:59 pm-10:39 am

1 stop8h 40m

$340

PeoriaOntario

PIA - ONT

PIAONT

Greater Peoria

Tue 8/18

12:20 pm-6:15 pm

2 stops7h 55m

Ontario

Tue 9/22

2:22 pm-11:15 pm

1 stop6h 53m

$354

MolineOntario

MLI - ONT

MLIONT

Moline Quad-City

Wed 7/1

4:46 pm-11:59 pm

1 stop9h 13m

Ontario

Fri 7/17

7:15 pm-10:39 am

2 stops13h 24m

$354

ChicagoOntario

MDW - ONT

MDWONT

Chicago Midway

Fri 8/7

2:00 pm-4:10 pm

Nonstop4h 10m

Ontario

Wed 8/12

6:50 am-5:10 pm

2 stops8h 20m

$358

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Sun 6/28

2:56 pm-3:08 pm

1 stop26h 12m

Ontario

Sun 7/5

3:40 pm-6:15 pm

1 stop24h 35m

$360

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Tue 6/23

8:08 pm-11:49 pm

1 stop5h 41m

Ontario

Wed 6/24

3:34 pm-2:06 pm

1 stop20h 32m

$362

ChicagoOntario

ORD - ONT

ORDONT

Chicago O'Hare Intl

Sat 8/8

8:18 pm-10:51 pm

Nonstop4h 33m

Ontario

Wed 8/12

1:56 pm-12:59 am

1 stop9h 03m

$365

ChicagoOntario

ORD - ONT

ORDONT

Chicago O'Hare Intl

Sat 9/5

8:06 pm-10:35 pm

Nonstop4h 29m

Ontario

Sat 9/12

1:56 pm-10:43 pm

1 stop6h 47m

$381

Flights are sorted by cheapest round-trip flights first.

Deals found on 6/2

Showing 1-10 of 60 resultsSorted by cheapest first
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6

Best time to book a flight from Illinois to Ontario

Have a flexible travel schedule? Discover the best time to fly to Ontario from Illinois with our price prediction graph.
Estimated round-trip price
Rates are based on past data. Find the cheapest month and day to book your flight based on your travel requirements, then search for cheap deals.

Cheapflights Insights

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

What is the cheapest month to book a flight from Illinois to Ontario?

Currently, December is the cheapest month in which you can book a flight from Illinois to Ontario (average of $107). Flying from Illinois to Ontario in May is currently the most expensive (average of $208). There are several factors that can impact the price of a flight, so comparing airlines, departure airports and flight times can provide users with more options.

What is the cheapest time of day to fly from IL to ONT?

Find hourly flight availability from Illinois to Ontario. Discover flight options and departure times throughout the day, allowing you to choose a departure time that suits your schedule. Data last updated June 7, 2026.

It’s typically best to fly out from Illinois to Ontario at noon. Doing so could potentially save you 29% on the flight price compared to flying in the morning, which is usually more expensive.

How much does it cost to fly round-trip from Illinois to Ontario?

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

The best time to book flights from Illinois to Ontario is 45 days before your desired departure date. The cost of your flight will likely increase significantly if you book two weeks in advance of your flight.

Related info for your journey

Find useful and relevant information for your journey from Illinois to Ontario. Access travel guides, tips, and recommendations to enhance your travel experience. Get information about local attractions, weather, transportation options, and more.

  • What airport do you fly into for flights to Ontario from Illinois?

    Located just 3.1 mi from the city center, Ontario (ONT) is the airport most travelers will use when flying to Ontario from Illinois.

  • How long is the flight from Illinois to Ontario?

    For as low as $255, Frontier can have you in Ontario from Illinois in 4h 10m. The distance between Illinois and Ontario is about 1701 mi. This flight may include one or multiple stops.

  • What are the cheapest airlines to fly from Illinois to Ontario one-way?

    $67 is the cheapest one-way deal found within the past few days, from Frontier. You may also be able to find cheap deals on American Airlines and Delta, with prices starting from $92 and $109, respectively.

  • What are the most popular routes from Illinois to Ontario?

    When deciding which route to take from Illinois to Ontario consider Chicago O'Hare Intl - Ontario, Lambert-St Louis - Ontario or Chicago Midway - Ontario as they are the most popular.

  • What are the cheapest flights from Illinois to Ontario?

    The cheapest flight price from Illinois to Ontario is $109. On average you can expect to pay $333. The most popular route, (Chicago O'Hare Intl - Ontario), can usually be booked for $254.

  • Can I find deals for flights from Illinois to Ontario that include hotel bookings?

    Yes. In addition to deals on Illinois to Ontario flights, Cheapflights offers vacation packages that include both flights and hotel.

  • How can I find direct flights from Illinois to Ontario?

    After entering your origin and destination, apply the non-stop filter on the search result page to find direct flights from Illinois to Ontario.

  • Can I find deals for business class flights from Illinois to Ontario?

    Yes. Cheapflights offers flight deals from Illinois to Ontario by cabin class. In addition to browsing deals, you can also filter by cabin class on the search results page after making a search.

  • What is the cheapest month to book a flight from Illinois to Ontario?

    Currently, December is the cheapest month in which you can book a flight from Illinois to Ontario (average of $107). Flying from Illinois to Ontario in May is currently the most expensive (average of $208). There are several factors that can impact the price of a flight, so comparing airlines, departure airports and flight times can provide users with more options.

See more FAQs

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Alternative routes for Illinois to Ontario

See prices for flight routes from nearby airports that may be better suited for you.
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Top 5 airlines flying from Illinois to Ontario

Discover the top 5 airlines that operate flights from Illinois to Ontario. Compare their services, reliability, and customer satisfaction ratings to choose the airline that best suits your travel preferences and needs. Over the last 7 days, Cheapflights users made 2,558,603 searches. Data last updated June 7, 2026.
AirlineCheapestAverageFlexibilityOn-time
FrontierCheapest$127Average$259FlexibilityNo cancel feeOn-time62%
SouthwestCheapest$218Average$522FlexibilityNo cancel feeOn-time63%
DeltaCheapest$236Average$385FlexibilityNo cancel feeOn-timeN/A
American AirlinesCheapest$300Average$505FlexibilityNo cancel feeOn-time71%
United AirlinesCheapest$329Average$554FlexibilityNo cancel feeOn-time69%

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