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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 1/19. Fares are subject to change and may not be available on all flights or dates of travel.
ORD — ONT
Jan 24 — Jan 311
Sat 1/24
Sat 1/31
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 December 25, 2025.

This CheapOair deal was found by Cheapflights users on 12/23. 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.
Wed 12/317:43 pmSTL - ONT
1 stop6h 16mFrontier
Thu 1/16:45 amONT - STL
1 stop25h 17mFrontier
Deal found 12/23$208
This Booking.com deal was found by Cheapflights users on 12/24. 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 12/317:43 pmSTL - ONT
1 stop6h 16mFrontier
Sat 1/103:21 pmONT - STL
1 stop27h 25mFrontier
Deal found 12/24$245
This Mytrip deal was found by Cheapflights users on 12/23. 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.
Wed 12/245:19 pmSTL - ONT
1 stop5h 58mFrontier
Wed 12/316:00 amONT - STL
1 stop8h 24mFrontier
Deal found 12/23$253
This Expedia deal was found by Cheapflights users on 12/24. 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 12/317:00 amORD - ONT
1 stop18h 59mFrontier
Mon 1/126:00 amONT - ORD
1 stop10h 45mFrontier
Deal found 12/24$254
This CheapOair deal was found by Cheapflights users on 12/24. 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.
Wed 12/317:43 pmSTL - ONT
1 stop6h 16mFrontier
Wed 1/710:45 amONT - STL
1 stop23h 27mFrontier
Deal found 12/24$258
This CheapOair deal was found by Cheapflights users on 12/23. 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.
Wed 12/317:00 amORD - ONT
1 stop18h 59mFrontier
Thu 1/16:45 amONT - ORD
1 stop15h 27mFrontier
Deal found 12/23$285
This Kiwi.com deal was found by Cheapflights users on 12/24. 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 12/319:34 pmORD - ONT
1 stop19h 47mMultiple Airlines
Tue 1/137:15 amONT - ORD
2 stops47h 03mMultiple Airlines
Deal found 12/24$310
This Orbitz deal was found by Cheapflights users on 12/24. 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 Orbitz is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sun 12/2810:50 pmMDW - ONT
1 stop27h 09mFrontier
Thu 1/158:02 amONT - MDW
1 stop7h 18mFrontier
Deal found 12/24$332
This CheapOair deal was found by Cheapflights users on 12/23. 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.
Wed 12/317:43 pmSTL - ONT
1 stop6h 16mFrontier
Fri 1/26:45 amONT - STL
1 stop25h 17mFrontier
Deal found 12/23$343
This Gotogate deal was found by Cheapflights users on 12/24. 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.
Wed 12/317:00 amORD - ONT
1 stop18h 59mFrontier
Sat 1/36:45 amONT - ORD
1 stop15h 27mFrontier
Deal found 12/24$353
This CheapOair deal was found by Cheapflights users on 12/24. 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.
Tue 12/3010:10 pmSTL - ONT
1 stop21h 05mFrontier
Wed 1/710:45 amONT - STL
1 stop23h 27mFrontier
Deal found 12/24$353
This Orbitz deal was found by Cheapflights users on 12/24. 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 Orbitz is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sun 12/289:34 pmORD - ONT
1 stop11h 50mFrontier
Thu 1/156:10 amONT - ORD
1 stop13h 14mFrontier
Deal found 12/24$362

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 December 25, 2025.

Most accurate provider

CheapOair
3 stars

Most trusted provider

CheapOair
3 stars

Round-trip from

$133
(Kiwi.com)

One-way from

$62
(Trip.com)

Popular in

December

Cheapest in

September

Average price

$377

Good round-trip deal

$372 or less

Good one-way deal

$266 or less
Provider with most accurate pricing for Chicago (CHI)-Los Angeles flight deals.
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Provider most trusted by Cheapflights users for Chicago (CHI)-Los Angeles flights.
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From Illinois to Ontario
Search Deals
One-way flight from Illinois to Ontario
Search Deals
Highest demand for flights based on searches. 12% potential increase in price ($39 potential increase over avg. RT price).
Search Deals
Cheapest flight prices on average. 3% potential price decrease ($10 potential savings vs. average RT price).
Search Deals
Average for round-trip flights in December 2025
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.
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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 December 25, 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

ChicagoOntario

MDW - ONT

MDWONT

Chicago Midway

Mon 1/12

3:00 pm-11:56 pm

1 stop10h 56m

Ontario

Thu 1/15

8:02 am-5:20 pm

1 stop7h 18m

$182

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Mon 1/26

1:40 pm-12:20 am

1 stop12h 40m

Ontario

Thu 1/29

11:04 am-9:06 pm

1 stop8h 02m

$182

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Sat 1/17

3:43 pm-10:59 pm

1 stop9h 16m

Ontario

Sat 1/24

7:15 am-2:46 pm

1 stop5h 31m

$183

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Mon 1/12

7:43 pm-11:56 pm

1 stop6h 13m

Ontario

Fri 1/23

10:18 am-8:48 pm

1 stop8h 30m

$207

ChicagoOntario

MDW - ONT

MDWONT

Chicago Midway

Thu 1/15

11:05 am-7:01 pm

1 stop9h 56m

Ontario

Fri 1/16

6:10 am-7:54 pm

1 stop11h 44m

$217

ChicagoOntario

MDW - ONT

MDWONT

Chicago Midway

Fri 1/9

3:05 pm-11:56 pm

1 stop10h 51m

Ontario

Mon 1/12

6:00 am-2:05 pm

1 stop6h 05m

$217

ChicagoOntario

MDW - ONT

MDWONT

Chicago Midway

Mon 1/12

3:00 pm-11:56 pm

1 stop10h 56m

Ontario

Sun 1/18

8:32 am-5:20 pm

1 stop6h 48m

$217

ChicagoOntario

MDW - ONT

MDWONT

Chicago Midway

Thu 1/15

11:05 am-7:01 pm

1 stop9h 56m

Ontario

Sun 1/18

8:32 am-5:20 pm

1 stop6h 48m

$217

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Sun 2/8

9:32 pm-12:10 pm

1 stop16h 38m

Ontario

Thu 2/19

7:22 pm-1:09 pm

2 stops15h 47m

$228

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Sun 1/18

10:09 pm-7:37 am

1 stop11h 28m

Ontario

Sun 1/25

6:20 am-12:50 pm

1 stop28h 30m

$237

Flights are sorted by cheapest round-trip flights first.

Deals found on 12/23

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, September is the cheapest month in which you can book a flight from Illinois to Ontario (average of $80). Flying from Illinois to Ontario in January is currently the most expensive (average of $124). 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 December 25, 2025.

It’s typically best to fly out from Illinois to Ontario in the evening. Doing so could potentially save you 27% on the flight price compared to flying in the morning, which is usually more expensive.

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

Use this chart to determine the cheapest time to fly round-trip from Illinois to Ontario. Price data was last updated on December 16, 2024.

Travelers seeking maximum savings on their Illinois to Ontario flight should consider departing on Saturday evenings when fares are most often at their lowest. Tuesday at noon flights should be avoided if possible as fares are typically the most expensive at this time.

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 $285, Frontier can have you in Ontario from Illinois in 8h 26m. The distance between Illinois and Ontario is about 1695 mi. This flight may include one or multiple stops.

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

    $75 is the cheapest one-way deal found within the past few days, from Frontier. You may also be able to find cheap deals on United Airlines and American Airlines, with prices starting from $113 and $123, 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 $255. On average you can expect to pay $456. The most popular route, (Chicago O'Hare Intl - Ontario), can usually be booked for $166.

  • 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, September is the cheapest month in which you can book a flight from Illinois to Ontario (average of $80). Flying from Illinois to Ontario in January is currently the most expensive (average of $124). 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 December 25, 2025.
AirlineCheapestAverageFlexibilityOn-time
FrontierCheapest$125Average$231FlexibilityNo cancel feeOn-time62%
American AirlinesCheapest$231Average$498FlexibilityNo cancel feeOn-time71%
United AirlinesCheapest$237Average$463FlexibilityNo cancel feeOn-time69%
SouthwestCheapest$246Average$430FlexibilityNo cancel feeOn-time63%
DeltaCheapest$256Average$256FlexibilityNo cancel feeOn-timeN/A

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