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Illinois

$66+ 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 1/29. Fares are subject to change and may not be available on all flights or dates of travel.
ONT — ORD
Feb 2 — Feb 91
Mon 2/2
Mon 2/9
1 adult, Economy
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Cheap 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 3, 2026.

This Trip.com deal was found by Cheapflights users on 1/2. 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 Trip.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 1/247:15 amONT - ORD
1 stop25h 42mFrontier
Sun 1/259:38 pmORD - ONT
1 stop16h 32mFrontier
Deal found 1/2$146
This Frontier deal was found by Cheapflights users on 1/2. 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 Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 1/247:15 amONT - STL
1 stop5h 31mFrontier
Sat 1/313:46 pmSTL - ONT
1 stop9h 38mFrontier
Deal found 1/2$148
This Kiwi.com deal was found by Cheapflights users on 1/2. 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.
Fri 1/3010:18 amONT - STL
1 stop8h 30mFrontier
Mon 2/21:40 pmSTL - ONT
1 stop12h 40mFrontier
Deal found 1/2$156
This Kiwi.com deal was found by Cheapflights users on 1/2. 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 2/178:35 amONT - STL
1 stop29h 18mFrontier
Fri 2/2010:11 pmSTL - ONT
1 stop23h 03mFrontier
Deal found 1/2$160
This Trip.com deal was found by Cheapflights users on 1/1. 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 Trip.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 1/2911:04 amONT - STL
1 stop8h 02mFrontier
Sat 1/313:46 pmSTL - ONT
1 stop9h 38mFrontier
Deal found 1/1$162
This Kiwi.com deal was found by Cheapflights users on 1/1. 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 1/317:15 amONT - ORD
1 stop25h 42mFrontier
Mon 2/167:19 pmORD - ONT
1 stop19h 52mFrontier
Deal found 1/1$162
This Kiwi.com deal was found by Cheapflights users on 1/1. 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.
Thu 2/56:20 amONT - ORD
1 stop10h 11mFrontier
Mon 2/167:19 pmORD - ONT
1 stop19h 52mFrontier
Deal found 1/1$163
This Frontier deal was found by Cheapflights users on 1/2. 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 Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 2/77:15 amONT - STL
1 stop5h 31mFrontier
Sat 2/142:51 pmSTL - ONT
1 stop11h 08mFrontier
Deal found 1/2$164
This Kiwi.com deal was found by Cheapflights users on 1/1. 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.
Thu 1/226:20 amONT - ORD
1 stop10h 11mFrontier
Sat 1/248:00 amORD - ONT
2 stops12h 40mFrontier
Deal found 1/1$164
This Frontier deal was found by Cheapflights users on 12/31. 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.
Wed 1/147:15 amONT - STL
1 stop5h 33mFrontier
Sat 1/313:46 pmSTL - ONT
1 stop9h 38mFrontier
Deal found 12/31$165
This Frontier deal was found by Cheapflights users on 1/2. 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 Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 1/247:15 amONT - STL
1 stop5h 31mFrontier
Mon 1/261:40 pmSTL - ONT
1 stop12h 40mFrontier
Deal found 1/2$166
This Kiwi.com deal was found by Cheapflights users on 1/1. 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 1/317:15 amONT - ORD
1 stop25h 42mFrontier
Tue 2/178:10 amORD - ONT
2 stops31h 01mFrontier
Deal found 1/1$166

Find flight deals from Ontario to Illinois

Keep the following information in mind while searching for Ontario to Illinois flight deals. Data was last updated January 3, 2026.

Most accurate provider

Justfly.com
3 stars

Most trusted provider

Justfly.com
3 stars

Round-trip from

$146
(Trip.com)

One-way from

$66
(Trip.com)

Popular in

December

Cheapest in

September

Average price

$308

Good round-trip deal

$352 or less

Good one-way deal

$183 or less
Provider with most accurate pricing for Los Angeles-Chicago (CHI) flight deals.
Search Deals
Provider most trusted by Cheapflights users for Los Angeles-Chicago (CHI) flights.
Search Deals
From Ontario to Illinois
Search Deals
One-way flight from Ontario to Illinois
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 ($8 potential savings vs. average RT price).
Search Deals
Average for round-trip flights in January 2026
Search Deals
Price to beat on a round-trip flight from Ontario to Illinois.
Search Deals
Price to beat on a one-way flight from Ontario to Illinois.
Search Deals

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 January 3, 2026.
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

Fri 1/30

10:18 am-8:48 pm

1 stop8h 30m

Lambert-St Louis

Mon 2/2

1:40 pm-12:20 am

1 stop12h 40m

$156

OntarioSt. Louis

ONT - STL

ONTSTL

Ontario

Sat 2/7

7:15 am-2:46 pm

1 stop5h 31m

Lambert-St Louis

Sat 2/14

2:51 pm-11:59 pm

1 stop11h 08m

$164

OntarioSt. Louis

ONT - STL

ONTSTL

Ontario

Wed 3/4

8:40 am-3:53 pm

1 stop5h 13m

Lambert-St Louis

Tue 3/10

8:06 pm-3:54 pm

1 stop21h 48m

$186

OntarioSt. Louis

ONT - STL

ONTSTL

Ontario

Tue 2/17

8:35 am-3:53 pm

1 stop29h 18m

Lambert-St Louis

Fri 2/20

1:59 pm-7:26 am

2 stops19h 27m

$190

OntarioSt. Louis

ONT - STL

ONTSTL

Ontario

Sat 1/24

7:15 am-2:46 pm

1 stop5h 31m

Lambert-St Louis

Fri 1/30

7:39 pm-12:20 am

1 stop6h 41m

$201

OntarioChicago

ONT - MDW

ONTMDW

Ontario

Wed 3/4

8:40 am-2:26 pm

2 stops27h 46m

Chicago Midway

Mon 3/9

10:00 am-8:53 pm

1 stop12h 53m

$229

OntarioSt. Louis

ONT - STL

ONTSTL

Ontario

Wed 2/25

8:40 am-3:53 pm

1 stop5h 13m

Lambert-St Louis

Sat 2/28

2:51 pm-11:59 pm

1 stop11h 08m

$235

OntarioSt. Louis

ONT - STL

ONTSTL

Ontario

Wed 2/11

3:22 pm-9:26 pm

1 stop28h 04m

Lambert-St Louis

Mon 2/16

1:54 pm-11:59 pm

1 stop12h 05m

$236

OntarioChicago

ONT - MDW

ONTMDW

Ontario

Fri 2/27

2:21 pm-3:19 pm

1 stop22h 58m

Chicago Midway

Mon 3/2

8:15 am-2:30 pm

1 stop8h 15m

$236

OntarioSt. Louis

ONT - STL

ONTSTL

Ontario

Fri 1/23

6:20 am-6:44 pm

1 stop10h 24m

Lambert-St Louis

Fri 1/30

7:39 pm-12:20 am

1 stop6h 41m

$253

Flights are sorted by cheapest round-trip flights first.

Deals found on 1/1

Showing 1-10 of 60 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, March is the cheapest month in which you can book a flight from Ontario to Illinois (average of $77). Flying from Ontario to Illinois in October is currently the most expensive (average of $147). 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 3, 2026.

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.

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 3, 2026.
Read through reviews of airlines operating flights from Ontario to Illinois, such as Southwest, Delta, and United Airlines. You can also see how each airline stacks up in terms of entertainment options, comfort, food, crew/service, and boarding process.
Southwest
8.0
Very good
4,257 reviews

Boarding

8.1

Entertainment

7.5

Overall

8.0

Food

7.0

Comfort

8.0

Crew

8.6

Reviews

1 / 20
10.0
Excellent

William Drew,Nov 2025

SJC - HNL

Flight crew was amazing! Usually they're very good on Southwest, but this crew went above and beyond. I have never ever seen so many rounds of drink service on a flight before.
Southwest
8.0
Very good
4,257 reviews
Southwest
8.0
Very good
4,257 reviews

Boarding

8.1

Entertainment

7.5

Overall

8.0

Food

7.0

Comfort

8.0

Crew

8.6

Reviews

1 / 20
10.0
Excellent

William Drew,Nov 2025

SJC - HNL

Flight crew was amazing! Usually they're very good on Southwest, but this crew went above and beyond. I have never ever seen so many rounds of drink service on a flight before.
Delta
7.9
Good
8,024 reviews
Southwest
8.0
Very good
4,257 reviews

Boarding

8.1

Entertainment

7.5

Overall

8.0

Food

7.0

Comfort

8.0

Crew

8.6

Reviews

1 / 20
10.0
Excellent

William Drew,Nov 2025

SJC - HNL

Flight crew was amazing! Usually they're very good on Southwest, but this crew went above and beyond. I have never ever seen so many rounds of drink service on a flight before.
United Airlines
7.4
Good
9,137 reviews
Southwest
8.0
Very good
4,257 reviews

Boarding

8.1

Entertainment

7.5

Overall

8.0

Food

7.0

Comfort

8.0

Crew

8.6

Reviews

1 / 20
10.0
Excellent

William Drew,Nov 2025

SJC - HNL

Flight crew was amazing! Usually they're very good on Southwest, but this crew went above and beyond. I have never ever seen so many rounds of drink service on a flight before.
American Airlines
7.2
Good
11,081 reviews
Southwest
8.0
Very good
4,257 reviews

Boarding

8.1

Entertainment

7.5

Overall

8.0

Food

7.0

Comfort

8.0

Crew

8.6

Reviews

1 / 20
10.0
Excellent

William Drew,Nov 2025

SJC - HNL

Flight crew was amazing! Usually they're very good on Southwest, but this crew went above and beyond. I have never ever seen so many rounds of drink service on a flight before.
Frontier
5.7
Fair
3,063 reviews
Southwest
8.0
Very good
4,257 reviews

Boarding

8.1

Entertainment

7.5

Overall

8.0

Food

7.0

Comfort

8.0

Crew

8.6

Reviews

1 / 20
10.0
Excellent

William Drew,Nov 2025

SJC - HNL

Flight crew was amazing! Usually they're very good on Southwest, but this crew went above and beyond. I have never ever seen so many rounds of drink service on a flight before.

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.

  • How long is the flight from Ontario to Illinois?

    For as low as $156, Frontier can have you in Illinois from Ontario in 8h 30m. The distance between Ontario and Illinois is about 1541 mi. Both multi-stop and nonstop flights can be found to your destination and back.

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

    $79 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 $102 and $112, 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 $386, our data shows the cheapest flight currently is $150. When looking at the most popular route, (Ontario - Chicago O'Hare Intl), you can expect to pay $146 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, March is the cheapest month in which you can book a flight from Ontario to Illinois (average of $77). Flying from Ontario to Illinois in October is currently the most expensive (average of $147). 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

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Top 5 airlines flying from Ontario to Illinois

Discover the top 5 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 3, 2026.
AirlineCheapestAverageFlexibilityOn-time
FrontierCheapest$110Average$225FlexibilityNo cancel feeOn-time62%
United AirlinesCheapest$227Average$459FlexibilityNo cancel feeOn-time69%
SouthwestCheapest$237Average$420FlexibilityNo cancel feeOn-time63%
DeltaCheapest$256Average$355FlexibilityNo cancel feeOn-timeN/A
American AirlinesCheapest$267Average$473FlexibilityNo cancel feeOn-time71%

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