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$89+ Cheap flights from Ontario (ONT) to Illinois

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 5/9. Fares are subject to change and may not be available on all flights or dates of travel.
ONT — ORD
Apr 22 — Apr 291
Tue 4/22
Tue 4/29
1 adult, Economy
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Cheap flight deals from Ontario to Illinois

Keep the following information in mind while searching for Ontario to Illinois flight deals. Data was last updated April 17, 2025.

Most accurate provider

FlightHub
3 stars

Most trusted provider

eDreams
3 stars

Round-trip from

$178
(Frontier)

One-way from

$89
(Frontier)

Popular in

June

Cheapest in

February

Average price

$311

Good round-trip deal

$317 or less

Good one-way deal

$158 or less
Provider with most accurate pricing for Los Angeles-Chicago (CHI) flight deals.
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From Ontario to Illinois
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One-way flight from Ontario to Illinois
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Highest demand for flights based on searches. 4% potential increase in price ($12 potential increase over avg. RT price).
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Cheapest flight prices on average. 1% potential price decrease ($4 potential savings vs. average RT price).
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Average for round-trip flights in April 2025
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Price to beat on a round-trip flight from Ontario to Illinois.
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Price to beat on a one-way flight from Ontario to Illinois.
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Find flight deals from Ontario to Illinois

Cheapest flights from Ontario to Illinois
Explore the most affordable flight options available from Ontario to Illinois. Find the lowest fares from popular airlines and budget airlines, with prices last updated on April 17, 2025.

This Frontier deal was found by Cheapflights users on 4/16. 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.
Tue 4/2212:59 amONT - STL
1 stop7h 02mFrontier
Sat 4/266:58 pmSTL - ONT
1 stop7h 01mFrontier
Deal found 4/16$178
This CheapOair deal was found by Cheapflights users on 4/16. 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 4/2310:44 amONT - MDW
1 stop26h 07mFrontier
Fri 4/256:15 amMDW - ONT
1 stop8h 59mFrontier
Deal found 4/16$218
This Frontier deal was found by Cheapflights users on 4/17. 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.
Fri 4/2512:11 pmONT - ORD
1 stop9h 26mFrontier
Sun 5/48:14 pmORD - ONT
1 stop13h 10mFrontier
Deal found 4/17$218
This United Airlines deal was found by Cheapflights users on 4/17. 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.
Sun 5/257:00 amONT - ORD
Nonstop4h 03mUnited Airlines
Sat 5/317:55 pmORD - ONT
Nonstop4h 31mUnited Airlines
Deal found 4/17$227
This Alaska Airlines deal was found by Cheapflights users on 4/16. 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 Alaska Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 8/217:10 amONT - ORD
1 stop19h 54mAlaska Airlines
Tue 8/268:42 pmORD - ONT
1 stop16h 03mAlaska Airlines
Deal found 4/16$246
This Southwest deal was found by Cheapflights users on 4/16. 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 Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 7/218:05 pmONT - MDW
1 stop6h 55mSouthwest
Fri 7/253:55 pmMDW - ONT
1 stop7h 55mSouthwest
Deal found 4/16$247
This American Airlines deal was found by Cheapflights users on 4/16. 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 American Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 5/197:25 pmONT - ORD
1 stop7h 48mAmerican Airlines
Wed 5/286:00 amORD - ONT
1 stop7h 50mAmerican Airlines
Deal found 4/16$247
This Delta deal was found by Cheapflights users on 4/16. 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 Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 6/412:18 pmONT - MDW
1 stop7h 09mDelta
Sat 6/76:00 amMDW - ONT
1 stop7h 08mDelta
Deal found 4/16$257
This Delta deal was found by Cheapflights users on 4/17. 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 Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 8/221:00 pmONT - ORD
1 stop7h 00mDelta
Thu 8/287:15 amORD - ONT
1 stop7h 08mDelta
Deal found 4/17$257
This American Airlines deal was found by Cheapflights users on 4/16. 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 American Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 5/911:59 pmONT - PIA
1 stop8h 49mAmerican Airlines
Tue 5/136:43 amPIA - ONT
1 stop9h 09mAmerican Airlines
Deal found 4/16$289
This American Airlines deal was found by Cheapflights users on 4/16. 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 American Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sun 5/252:44 pmONT - STL
1 stop6h 01mAmerican Airlines
Tue 6/32:19 pmSTL - ONT
1 stop6h 04mAmerican Airlines
Deal found 4/16$306
This Delta deal was found by Cheapflights users on 4/16. 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 Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 5/74:57 pmONT - STL
1 stop5h 36mDelta
Wed 5/217:19 pmSTL - ONT
1 stop6h 23mDelta
Deal found 4/16$307

Cheapflights Fare Finder

Customize your flight search to find flights from Ontario to Illinois 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 April 17, 2025.
Use the filters below to find and compare flights from Ontario to Illinois that are best for you.

Fly from

Ontario

Fly to

Illinois

Route

Depart

Return

Price

OntarioSt. Louis

ONT - STL

ONTSTL

Ontario

Tue 4/29

12:59 am-10:01 am

1 stop7h 02m

Lambert-St Louis

Sat 5/3

8:15 pm-11:59 pm

1 stop5h 44m

$178

OntarioChicago

ONT - MDW

ONTMDW

Ontario

Thu 5/22

5:26 pm-3:00 pm

1 stop19h 34m

Chicago Midway

Sat 5/24

2:44 pm-9:15 am

1 stop20h 31m

$218

OntarioChicago

ONT - ORD

ONTORD

Ontario

Mon 4/28

2:42 pm-5:14 am

1 stop12h 32m

Chicago O'Hare Intl

Thu 5/1

8:14 pm-7:24 am

1 stop13h 10m

$218

OntarioChicago

ONT - ORD

ONTORD

Ontario

Sat 7/26

7:00 am-1:03 pm

Nonstop4h 03m

Chicago O'Hare Intl

Thu 7/31

7:40 pm-10:11 pm

Nonstop4h 31m

$227

OntarioChicago

ONT - ORD

ONTORD

Ontario

Thu 8/21

7:10 am-5:04 am

1 stop19h 54m

Chicago O'Hare Intl

Tue 8/26

8:42 pm-10:45 am

1 stop16h 03m

$246

OntarioChicago

ONT - MDW

ONTMDW

Ontario

Mon 7/21

8:05 pm-5:00 am

1 stop6h 55m

Chicago Midway

Fri 7/25

3:55 pm-9:50 pm

1 stop7h 55m

$247

OntarioChicago

ONT - ORD

ONTORD

Ontario

Mon 5/19

11:59 pm-11:08 am

1 stop9h 09m

Chicago O'Hare Intl

Thu 5/29

1:34 pm-9:05 pm

1 stop9h 31m

$247

OntarioChicago

ONT - MDW

ONTMDW

Ontario

Wed 6/4

12:18 pm-9:27 pm

1 stop7h 09m

Chicago Midway

Sat 6/7

6:00 am-11:08 am

1 stop7h 08m

$257

OntarioChicago

ONT - ORD

ONTORD

Ontario

Fri 8/22

1:00 pm-10:00 pm

1 stop7h 00m

Chicago O'Hare Intl

Thu 8/28

7:15 am-12:23 pm

1 stop7h 08m

$257

OntarioPeoria

ONT - PIA

ONTPIA

Ontario

Fri 5/9

11:59 pm-10:48 am

1 stop8h 49m

Greater Peoria

Tue 5/13

6:43 am-1:52 pm

1 stop9h 09m

$289

Flights are sorted by cheapest round-trip flights first.

Deals found on 4/16

Showing 1-10 of 53 results
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Best time to book a flight from Ontario to Illinois

Have a flexible travel schedule? Discover the best time to fly to Illinois from Ontario 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 Ontario to Illinois

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

Currently, August is the cheapest month in which you can book a flight from Ontario to Illinois (average of $245). Flying from Ontario to Illinois in March is currently the most expensive (average of $321). 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 ONT to IL?

Find hourly flight availability from Ontario to Illinois. Discover flight options and departure times throughout the day, allowing you to choose a departure time that suits your schedule. Data last updated April 17, 2025.

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

Rainfall in Illinois by month

Plan your trip to Illinois by taking into account the average rainfall totals by month.

In terms of precipitation, rainfall in Illinois ranges from 1.7 - 4.9 inches per month. August is typically the wettest month, when rainfall can reach 4.9 in. January is typically the driest time to visit Illinois when rainfall is around 1.7 in.

Temperature in Illinois by month

Plan your trip to Illinois by taking into account the average temperature totals by month.

If weather is an important factor for your trip to Illinois, use this chart to help with planning. For those seeking warmer temperatures, July is the ideal time of year to visit, when temperatures reach an average of 73.4 F. Travelers looking to avoid the cold should look outside of January, when temperatures are typically at their lowest (around 23.0 F).

Reviews of airlines servicing Illinois

Get insights into the airlines that provide service to Illinois. Read reviews, discover amenities, and learn about the overall travel experience offered by airlines. Use this information to make informed decisions when choosing an airline for your flight to Illinois. Reviews last updated April 17, 2025.
Get a feel of what it's like to fly with Alaska Airlines, Southwest and Delta from Ontario to Illinois by reading reviews from past customers. In addition to providing an overall rating, users have also rated airlines in terms of entertainment options, comfort, food, crew/service, and boarding process.
Alaska Airlines
8.0
Very good
9,882 reviews

Boarding

8.2

Overall

8.0

Food

7.1

Crew

8.5

Comfort

7.9

Entertainment

7.1

Reviews

1 / 20
10.0
Excellent

Cheri,Jan 2025

FAT - SEA

Very friendly. I really liked that they had water for us in cartons not plastic. Impressed with Alaska Airlines, First time I had flown them
Alaska Airlines
8.0
Very good
9,882 reviews
Alaska Airlines
8.0
Very good
9,882 reviews

Boarding

8.2

Overall

8.0

Food

7.1

Crew

8.5

Comfort

7.9

Entertainment

7.1

Reviews

1 / 20
10.0
Excellent

Cheri,Jan 2025

FAT - SEA

Very friendly. I really liked that they had water for us in cartons not plastic. Impressed with Alaska Airlines, First time I had flown them
Southwest
8.0
Very good
4,280 reviews
Alaska Airlines
8.0
Very good
9,882 reviews

Boarding

8.2

Overall

8.0

Food

7.1

Crew

8.5

Comfort

7.9

Entertainment

7.1

Reviews

1 / 20
10.0
Excellent

Cheri,Jan 2025

FAT - SEA

Very friendly. I really liked that they had water for us in cartons not plastic. Impressed with Alaska Airlines, First time I had flown them
Delta
8.0
Very good
7,917 reviews
Alaska Airlines
8.0
Very good
9,882 reviews

Boarding

8.2

Overall

8.0

Food

7.1

Crew

8.5

Comfort

7.9

Entertainment

7.1

Reviews

1 / 20
10.0
Excellent

Cheri,Jan 2025

FAT - SEA

Very friendly. I really liked that they had water for us in cartons not plastic. Impressed with Alaska Airlines, First time I had flown them
Hawaiian Airlines
7.9
Good
2,382 reviews
Alaska Airlines
8.0
Very good
9,882 reviews

Boarding

8.2

Overall

8.0

Food

7.1

Crew

8.5

Comfort

7.9

Entertainment

7.1

Reviews

1 / 20
10.0
Excellent

Cheri,Jan 2025

FAT - SEA

Very friendly. I really liked that they had water for us in cartons not plastic. Impressed with Alaska Airlines, First time I had flown them
United Airlines
7.4
Good
8,667 reviews
Alaska Airlines
8.0
Very good
9,882 reviews

Boarding

8.2

Overall

8.0

Food

7.1

Crew

8.5

Comfort

7.9

Entertainment

7.1

Reviews

1 / 20
10.0
Excellent

Cheri,Jan 2025

FAT - SEA

Very friendly. I really liked that they had water for us in cartons not plastic. Impressed with Alaska Airlines, First time I had flown them

Related info for your journey

Find useful and relevant information for your journey from Ontario to Illinois. 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 from for flights from Ontario to Illinois?

    Ontario (ONT), located 3.1 mi from the city center, is the airport you fly out of when you book flights from Ontario to Illinois.

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

    $89 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 Alaska Airlines, with prices starting from $114 and $123, respectively.

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

    The most popular flight routes from Ontario to Illinois are Ontario - Chicago O'Hare Intl, Ontario - Chicago Midway and Ontario - Lambert-St Louis.

  • What are the cheapest flights from Ontario to Illinois?

    While on average a flight from Ontario to Illinois is generally $643, our data shows the cheapest flight currently is $113. When looking at the most popular route, (Ontario - Chicago O'Hare Intl), you can expect to pay $201 for that flight.

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

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

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

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

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

    Yes. Cheapflights offers flight deals from Ontario to Illinois 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 Ontario to Illinois?

    Currently, August is the cheapest month in which you can book a flight from Ontario to Illinois (average of $245). Flying from Ontario to Illinois in March is currently the most expensive (average of $321). 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 Ontario to Illinois

See prices for flight routes from nearby airports that may be better suited for you.
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Top 7 airlines flying from Ontario to Illinois

Discover the top 7 airlines that operate flights from Ontario to Illinois. 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 April 17, 2025.
AirlineCheapestAverageFlexibilityOn-time
Spirit AirlinesCheapest$74Average$177FlexibilityNo cancel feeOn-time65%
FrontierCheapest$108Average$207FlexibilityNo cancel feeOn-time62%
Alaska AirlinesCheapest$161Average$438FlexibilityNo cancel feeOn-time75%
United AirlinesCheapest$227Average$491FlexibilityNo cancel feeOn-time69%
DeltaCheapest$241Average$417FlexibilityNo cancel feeOn-timeN/A
American AirlinesCheapest$246Average$505FlexibilityNo cancel feeOn-time71%
SouthwestCheapest$246Average$455FlexibilityNo cancel feeOn-time63%

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