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$62+ 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 10/7. Fares are subject to change and may not be available on all flights or dates of travel.
ORD — ONT
Oct 11 — Oct 181
Sat 10/11
Sat 10/18
1 adult, Economy
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Cheap flight deals from Illinois to Ontario

Keep the following information in mind while searching for Illinois to Ontario flight deals. Data was last updated September 11, 2025.

Round-trip from

$129
(Kiwi.com)

One-way from

$62
(Trip.com)

Popular in

December

Cheapest in

September

Average price

$229

Good round-trip deal

$329 or less

Good one-way deal

$205 or less
From Illinois to Ontario
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One-way flight from Illinois to Ontario
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Highest demand for flights based on searches. 10% potential increase in price ($31 potential increase over avg. RT price).
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Cheapest flight prices on average. 3% potential price decrease ($10 potential savings vs. average RT price).
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Average for round-trip flights in September 2025
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Price to beat on a round-trip flight from Illinois to Ontario.
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Price to beat on a one-way flight from Illinois to Ontario.
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Find 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 September 11, 2025.

This Kiwi.com deal was found by Cheapflights users on 9/9. 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 10/157:15 amORD - ONT
1 stop18h 35mFrontier
Wed 11/126:53 amONT - ORD
1 stop15h 19mFrontier
Deal found 9/9$129
This Kiwi.com deal was found by Cheapflights users on 9/10. 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 11/17:15 amORD - ONT
1 stop18h 35mFrontier
Wed 11/56:53 amONT - ORD
1 stop15h 19mFrontier
Deal found 9/10$132
This Cheapflightsfares deal was found by Cheapflights users on 9/8. 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 Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 11/14:51 pmSTL - ONT
1 stop5h 51mFrontier
Thu 11/66:00 amONT - STL
1 stop5h 57mFrontier
Deal found 9/8$142
This Kiwi.com deal was found by Cheapflights users on 9/9. 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 10/157:15 amORD - ONT
1 stop18h 35mFrontier
Sat 11/156:53 amONT - ORD
1 stop15h 19mFrontier
Deal found 9/9$143
This Mytrip deal was found by Cheapflights users on 9/10. 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 Mytrip is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 9/269:35 pmSTL - ONT
1 stop17h 08mFrontier
Sun 9/288:59 pmONT - STL
1 stop10h 07mFrontier
Deal found 9/10$143
This Booking.com deal was found by Cheapflights users on 9/11. 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.
Mon 10/139:59 pmSTL - ONT
1 stop24h 43mFrontier
Thu 10/166:05 amONT - STL
1 stop27h 38mFrontier
Deal found 9/11$145
This CheapOair deal was found by Cheapflights users on 9/10. 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 CheapOair is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 11/17:15 amORD - ONT
1 stop5h 55mFrontier
Sun 11/25:53 amONT - ORD
1 stop15h 19mFrontier
Deal found 9/10$148
This Booking.com deal was found by Cheapflights users on 9/11. 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 10/297:20 amORD - ONT
1 stop18h 30mFrontier
Sat 11/112:05 pmONT - ORD
1 stop10h 07mFrontier
Deal found 9/11$149
This CheapOair deal was found by Cheapflights users on 9/10. 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 CheapOair is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 11/712:30 pmMDW - ONT
1 stop24h 40mFrontier
Sun 11/96:53 amONT - MDW
1 stop26h 37mFrontier
Deal found 9/10$150
This Booking.com deal was found by Cheapflights users on 9/11. 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.
Fri 10/3112:30 pmMDW - ONT
1 stop24h 40mFrontier
Sun 11/25:53 amONT - MDW
1 stop26h 37mFrontier
Deal found 9/11$151
This Kiwi.com deal was found by Cheapflights users on 9/11. 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 10/287:14 amORD - ONT
1 stop18h 36mFrontier
Tue 11/46:53 amONT - ORD
1 stop15h 19mFrontier
Deal found 9/11$152
This Cheapflightsfares deal was found by Cheapflights users on 9/9. 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 Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sun 9/2810:39 amSTL - ONT
1 stop6h 45mFrontier
Thu 10/26:00 amONT - STL
1 stop5h 53mFrontier
Deal found 9/9$152

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 September 11, 2025.
Use the filters below to find and compare flights from Illinois to Ontario that are best for you.

Fly from

Illinois

Fly to

Ontario

Route

Depart

Return

Price

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Sat 11/15

4:51 pm-8:42 pm

1 stop5h 51m

Ontario

Sun 11/16

7:47 am-5:28 pm

1 stop7h 41m

$144

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Mon 10/13

9:59 pm-8:42 pm

1 stop24h 43m

Ontario

Wed 10/15

6:53 am-9:07 am

1 stop24h 14m

$145

ChicagoOntario

MDW - ONT

MDWONT

Chicago Midway

Fri 10/31

12:30 pm-11:10 am

1 stop24h 40m

Ontario

Sun 11/2

5:53 am-10:30 am

1 stop26h 37m

$151

ChicagoOntario

MDW - ONT

MDWONT

Chicago Midway

Fri 10/31

12:30 pm-11:10 am

1 stop24h 40m

Ontario

Sun 11/9

6:53 am-11:30 am

1 stop26h 37m

$151

ChicagoOntario

MDW - ONT

MDWONT

Chicago Midway

Thu 10/16

10:30 am-5:54 pm

1 stop9h 24m

Ontario

Mon 10/20

6:53 am-12:24 am

1 stop15h 31m

$154

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Thu 9/25

10:49 am-3:29 pm

1 stop6h 40m

Ontario

Thu 9/25

8:59 pm-9:06 am

1 stop10h 07m

$154

ChicagoOntario

ORD - ONT

ORDONT

Chicago O'Hare Intl

Mon 9/22

9:54 pm-9:56 pm

1 stop26h 02m

Ontario

Mon 9/29

4:08 pm-9:28 pm

1 stop27h 20m

$154

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Fri 9/26

2:38 pm-9:55 pm

1 stop9h 17m

Ontario

Sat 9/27

8:59 pm-9:06 am

1 stop10h 07m

$166

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Fri 9/26

2:38 pm-9:55 pm

1 stop9h 17m

Ontario

Wed 10/1

8:59 pm-9:06 am

1 stop10h 07m

$166

ChicagoOntario

MDW - ONT

MDWONT

Chicago Midway

Thu 10/16

6:24 pm-11:50 pm

1 stop7h 26m

Ontario

Sun 10/26

6:53 am-11:16 am

1 stop26h 23m

$168

Flights are sorted by cheapest round-trip flights first.

Deals found on 9/10

Showing 1-10 of 60 results
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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, August is the cheapest month in which you can book a flight from Illinois to Ontario (average of $246). Flying from Illinois to Ontario in March is currently the most expensive (average of $328). 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 September 11, 2025.

Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Illinois to Ontario as you normally would.

Weekly flight availability from Illinois to Ontario

Explore weekly flight availability from Illinois to Ontario. Discover flights operating on different days of the week, giving you the flexibility to choose a travel day that best fits your plans. Compare info to find the most convenient option for your journey. Data last updated September 11, 2025.

The most flights from USIL to ONT are scheduled on a Monday (1 on average). You will have fewer flight options on Monday, which is when the least amount of flights are scheduled (1 on average).

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 $144, Frontier can have you in Ontario from Illinois in 5h 51m. The distance between Illinois and Ontario is about 1541 mi. This flight may include one or multiple stops.

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

    $73 is the cheapest one-way deal found within the past few days, from Frontier. You may also be able to find cheap deals on Southwest and United Airlines, with prices starting from $92 and $98, 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, Chicago Midway - Ontario or Lambert-St Louis - 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 $148. On average you can expect to pay $351. The most popular route, (Chicago O'Hare Intl - Ontario), can usually be booked for $148.

  • 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, August is the cheapest month in which you can book a flight from Illinois to Ontario (average of $246). Flying from Illinois to Ontario in March is currently the most expensive (average of $328). 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 September 11, 2025.
AirlineCheapestAverageFlexibilityOn-time
FrontierCheapest$124Average$212FlexibilityNo cancel feeOn-time62%
American AirlinesCheapest$231Average$571FlexibilityNo cancel feeOn-time71%
United AirlinesCheapest$237Average$411FlexibilityNo cancel feeOn-time69%
DeltaCheapest$246Average$256FlexibilityNo cancel feeOn-timeN/A
SouthwestCheapest$246Average$464FlexibilityNo cancel feeOn-time63%

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