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$55+ 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 4/15. Fares are subject to change and may not be available on all flights or dates of travel.
ONT — ORD
Jan 22 — Jan 291
Wed 1/22
Wed 1/29
1 adult, Economy
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Cheap flight deals from Ontario to Illinois

Discover tips and strategies to find the most affordable flight options for your journey from Ontario (ONT) to Illinois (USIL). Learn about various techniques such as flexible date searches, comparing prices across and setting up price alerts. Use these methods to find the cheapest flights available for your travel needs. Data last updated January 17, 2025.

Round-trip from

$110
(Frontier)

One-way from

$55
(Cheapflightsfares)
From Ontario to Illinois
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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 January 17, 2025.

This Frontier deal was found by Cheapflights users on 1/15. 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 1/307:56 amONT - STL
1 stop9h 35mFrontier
Sat 2/17:09 pmSTL - ONT
1 stop6h 38mFrontier
Deal found 1/15$110
This Mytrip deal was found by Cheapflights users on 1/16. 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 Mytrip is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 2/710:40 amONT - MDW
1 stop11h 37mFrontier
Mon 2/107:15 amMDW - ONT
1 stop12h 13mFrontier
Deal found 1/16$158
This Booking.com deal was found by Cheapflights users on 1/16. 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 Booking.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 2/1312:59 amONT - ORD
1 stop21h 45mFrontier
Sun 2/237:59 pmORD - ONT
1 stop13h 27mFrontier
Deal found 1/16$160
This eDestinos deal was found by Cheapflights users on 1/16. 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 eDestinos is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 2/1710:34 amONT - ORD
2 stops31h 58mMultiple Airlines
Tue 2/257:51 pmORD - ONT
1 stop21h 28mMultiple Airlines
Deal found 1/16$194
This American Airlines deal was found by Cheapflights users on 1/16. 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 2/1611:59 pmONT - ORD
1 stop6h 24mAmerican Airlines
Thu 2/271:54 pmORD - ONT
1 stop9h 08mAmerican Airlines
Deal found 1/16$247
This KAYAK deal was found by Cheapflights users on 1/16. 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 KAYAK is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 2/251:05 pmONT - ORD
1 stop8h 43mDelta
Fri 2/285:45 amORD - ONT
1 stop8h 10mDelta
Deal found 1/16$253
This Delta deal was found by Cheapflights users on 1/16. 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.
Tue 2/111:00 pmONT - MDW
1 stop7h 20mDelta
Tue 2/186:00 amMDW - ONT
1 stop7h 55mDelta
Deal found 1/16$269
This Southwest deal was found by Cheapflights users on 1/16. 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.
Sat 2/157:05 amONT - MDW
Nonstop3h 45mSouthwest
Mon 2/179:00 amMDW - ONT
Nonstop4h 30mSouthwest
Deal found 1/16$281
This Alaska Airlines deal was found by Cheapflights users on 1/16. 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.
Tue 4/156:00 amONT - ORD
1 stop9h 55mAlaska Airlines
Fri 4/183:16 pmORD - ONT
1 stop10h 43mAlaska Airlines
Deal found 1/16$287
This Expedia deal was found by Cheapflights users on 1/15. 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.
Thu 1/307:56 amONT - STL
1 stop9h 35mMultiple Airlines
Sat 2/16:44 amSTL - ONT
2 stops12h 20mMultiple Airlines
Deal found 1/15$314
This United Airlines deal was found by Cheapflights users on 1/16. 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 United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 5/214:10 pmONT - ORD
1 stop5h 55mUnited Airlines
Sat 5/3112:45 pmORD - ONT
1 stop6h 40mUnited Airlines
Deal found 1/16$337
This Delta deal was found by Cheapflights users on 1/15. 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 2/51:00 pmONT - STL
1 stop8h 36mDelta
Tue 2/186:00 amSTL - ONT
1 stop7h 55mDelta
Deal found 1/15$343

Find flights from Ontario to Illinois within your budget

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 January 17, 2025.

Fly from

Any airport

Fly to

Any airport

Route

Depart

Return

Price

OntarioSt. Louis

ONT - STL

ONTSTL

Ontario

Thu 1/30

7:56 am-7:31 pm

1 stop9h 35m

Lambert-St Louis

Sat 2/1

7:09 pm-11:47 pm

1 stop6h 38m

$110

OntarioChicago

ONT - MDW

ONTMDW

Ontario

Fri 2/7

10:40 am-12:17 am

1 stop11h 37m

Chicago Midway

Mon 2/10

7:15 am-5:28 pm

1 stop12h 13m

$158

OntarioChicago

ONT - ORD

ONTORD

Ontario

Thu 2/13

12:59 am-12:44 am

1 stop21h 45m

Chicago O'Hare Intl

Sun 2/23

7:59 pm-7:26 am

1 stop13h 27m

$160

OntarioChicago

ONT - ORD

ONTORD

Ontario

Mon 2/17

10:34 am-8:32 pm

2 stops31h 58m

Chicago O'Hare Intl

Tue 2/25

7:51 pm-3:19 pm

1 stop21h 28m

$194

OntarioChicago

ONT - ORD

ONTORD

Ontario

Sun 2/16

11:59 pm-8:23 am

1 stop6h 24m

Chicago O'Hare Intl

Thu 2/27

1:54 pm-9:02 pm

1 stop9h 08m

$247

OntarioChicago

ONT - ORD

ONTORD

Ontario

Tue 2/25

1:05 pm-11:48 pm

1 stop8h 43m

Chicago O'Hare Intl

Fri 2/28

5:45 am-11:55 am

1 stop8h 10m

$253

OntarioChicago

ONT - MDW

ONTMDW

Ontario

Thu 2/27

7:05 am-4:20 pm

1 stop7h 15m

Chicago Midway

Tue 3/4

10:19 am-10:32 pm

2 stops14h 13m

$262

OntarioChicago

ONT - MDW

ONTMDW

Ontario

Sat 2/15

7:05 am-12:50 pm

Nonstop3h 45m

Chicago Midway

Sat 2/22

8:10 am-10:45 am

Nonstop4h 35m

$281

OntarioChicago

ONT - ORD

ONTORD

Ontario

Tue 4/15

6:00 am-5:55 pm

1 stop9h 55m

Chicago O'Hare Intl

Fri 4/18

3:16 pm-11:59 pm

1 stop10h 43m

$287

OntarioSt. Louis

ONT - STL

ONTSTL

Ontario

Thu 1/30

7:56 am-7:31 pm

1 stop9h 35m

Lambert-St Louis

Sat 2/1

6:44 am-5:04 pm

2 stops12h 20m

$314

Flights are sorted by cheapest round-trip flights first.

Deals found on 1/16

Showing 1-10 of 46 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.

Travel insights for flights from Ontario to Illinois

Get recent, data-driven insights about flights from Ontario to Illinois including ideal travel times, pricing trends, and more.

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 $320). 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 January 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 January 17, 2025.
Get a feel of what it's like to fly with United Airlines, Delta and Alaska Airlines 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.
Southwest
8.1
Very good
4,659 reviews

Overall

8.1

Entertainment

7.7

Boarding

8.2

Comfort

8.1

Crew

8.7

Food

7.2

Reviews

1 / 10

My original flight was delayed so they found this flight for me so I could arrive at a reasonable time

Southwest
8.1
Very good
4,659 reviews
Southwest
8.1
Very good
4,659 reviews

Overall

8.1

Entertainment

7.7

Boarding

8.2

Comfort

8.1

Crew

8.7

Food

7.2

Reviews

1 / 10

My original flight was delayed so they found this flight for me so I could arrive at a reasonable time

Alaska Airlines
8.0
Very good
9,681 reviews
Southwest
8.1
Very good
4,659 reviews

Overall

8.1

Entertainment

7.7

Boarding

8.2

Comfort

8.1

Crew

8.7

Food

7.2

Reviews

1 / 10

My original flight was delayed so they found this flight for me so I could arrive at a reasonable time

Delta
8.0
Very good
8,511 reviews
Southwest
8.1
Very good
4,659 reviews

Overall

8.1

Entertainment

7.7

Boarding

8.2

Comfort

8.1

Crew

8.7

Food

7.2

Reviews

1 / 10

My original flight was delayed so they found this flight for me so I could arrive at a reasonable time

United Airlines
7.4
Good
8,964 reviews
Southwest
8.1
Very good
4,659 reviews

Overall

8.1

Entertainment

7.7

Boarding

8.2

Comfort

8.1

Crew

8.7

Food

7.2

Reviews

1 / 10

My original flight was delayed so they found this flight for me so I could arrive at a reasonable time

American Airlines
7.2
Good
10,000 reviews
Southwest
8.1
Very good
4,659 reviews

Overall

8.1

Entertainment

7.7

Boarding

8.2

Comfort

8.1

Crew

8.7

Food

7.2

Reviews

1 / 10

My original flight was delayed so they found this flight for me so I could arrive at a reasonable time

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?

    $55 is the cheapest one-way deal found within the past few days, from Frontier. You may also be able to find cheap deals on Alaska Airlines and American Airlines, with prices starting from $123 and $124, 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.

  • 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 $320). 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.

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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 January 17, 2025.
AirlineCheapestAverageFlexibilityOn-time
Spirit AirlinesCheapest$92Average$177FlexibilityNo cancel feeOn-time65%
FrontierCheapest$108Average$213FlexibilityNo cancel feeOn-time62%
Alaska AirlinesCheapest$161Average$438FlexibilityNo cancel feeOn-time75%
DeltaCheapest$236Average$446FlexibilityNo cancel feeOn-timeN/A
United AirlinesCheapest$246Average$516FlexibilityNo cancel feeOn-time69%
American AirlinesCheapest$247Average$586FlexibilityNo cancel feeOn-time71%
SouthwestCheapest$358Average$505FlexibilityNo cancel feeOn-time63%
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