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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 4 — Feb 111
Wed 2/4
Wed 2/11
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 5, 2026.

This Kiwi.com deal was found by Cheapflights users on 1/3. 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 1/296:20 amONT - ORD
1 stop10h 11mFrontier
Sun 2/19:38 pmORD - ONT
1 stop19h 03mFrontier
Deal found 1/3$135
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 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 Travelocity deal was found by Cheapflights users on 1/4. 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 Travelocity is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 2/288:21 amONT - ORD
1 stop12h 56mFrontier
Mon 3/27:19 pmORD - ONT
1 stop19h 52mFrontier
Deal found 1/4$164
This Kiwi.com deal was found by Cheapflights users on 1/3. 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 2/47:15 amONT - ORD
2 stops29h 30mFrontier
Fri 2/612:07 pmORD - ONT
1 stop14h 13mFrontier
Deal found 1/3$175
This Booking.com deal was found by Cheapflights users on 1/3. 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 2/182:06 pmONT - ORD
1 stop28h 57mFrontier
Thu 2/266:34 pmORD - ONT
1 stop23h 27mFrontier
Deal found 1/3$177
This Frontier deal was found by Cheapflights users on 1/3. 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 2/511:04 amONT - STL
1 stop8h 02mFrontier
Mon 2/91:40 pmSTL - ONT
1 stop12h 40mFrontier
Deal found 1/3$180
This Frontier deal was found by Cheapflights users on 1/3. 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 1/226:20 amONT - ORD
1 stop10h 11mFrontier
Thu 1/297:41 pmORD - ONT
1 stop6h 39mFrontier
Deal found 1/3$180
This CheapOair deal was found by Cheapflights users on 1/4. 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.
Thu 2/196:05 amONT - ORD
1 stop15h 09mFrontier
Mon 2/237:19 pmORD - ONT
1 stop20h 33mFrontier
Deal found 1/4$181
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.
Sat 2/218:21 amONT - ORD
1 stop12h 56mFrontier
Sat 2/284:29 pmORD - ONT
2 stops31h 00mFrontier
Deal found 1/2$182
This Trip.com deal was found by Cheapflights users on 1/4. 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.
Wed 1/283:07 pmONT - ORD
2 stops20h 30mFrontier
Sun 2/19:38 pmORD - ONT
1 stop16h 32mFrontier
Deal found 1/4$184

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 5, 2026.

Most accurate provider

Justfly.com
3 stars

Most trusted provider

Justfly.com
3 stars

Round-trip from

$135
(Kiwi.com)

One-way from

$66
(Trip.com)

Popular in

December

Cheapest in

September

Average price

$352

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.
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From Ontario to Illinois
Search Deals
One-way flight from Ontario to Illinois
Search Deals
Highest demand for flights based on searches. 12% potential increase in price ($43 potential increase over avg. RT price).
Search Deals
Cheapest flight prices on average. 1% potential price decrease ($5 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 5, 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

Thu 2/5

3:22 pm-8:48 pm

1 stop27h 26m

Lambert-St Louis

Sun 2/8

12:03 pm-12:20 am

1 stop14h 17m

$216

OntarioSt. Louis

ONT - STL

ONTSTL

Ontario

Thu 1/22

11:04 am-9:06 pm

1 stop8h 02m

Lambert-St Louis

Fri 1/23

7:39 pm-12:20 am

1 stop6h 41m

$236

OntarioSt. Louis

ONT - STL

ONTSTL

Ontario

Fri 1/23

6:20 am-6:44 pm

1 stop10h 24m

Lambert-St Louis

Sun 1/25

9:27 pm-2:41 pm

1 stop19h 14m

$251

OntarioChicago

ONT - MDW

ONTMDW

Ontario

Thu 1/15

8:02 am-5:20 pm

1 stop7h 18m

Chicago Midway

Sun 1/18

11:05 am-7:01 pm

1 stop9h 56m

$257

OntarioSt. Louis

ONT - STL

ONTSTL

Ontario

Fri 1/16

6:10 am-6:32 pm

1 stop10h 22m

Lambert-St Louis

Sun 1/18

1:35 pm-5:44 pm

1 stop6h 09m

$270

OntarioChicago

ONT - MDW

ONTMDW

Ontario

Fri 1/16

6:10 am-7:54 pm

1 stop11h 44m

Chicago Midway

Sun 1/18

11:05 am-7:01 pm

1 stop9h 56m

$270

OntarioSt. Louis

ONT - STL

ONTSTL

Ontario

Sat 2/14

10:20 pm-9:06 am

1 stop8h 46m

Lambert-St Louis

Tue 2/24

2:22 pm-10:37 pm

2 stops10h 15m

$304

OntarioMoline

ONT - MLI

ONTMLI

Ontario

Fri 2/6

12:41 pm-10:33 pm

1 stop7h 52m

Moline Quad-City

Sun 2/8

5:51 am-11:31 am

1 stop7h 40m

$309

Flights are sorted by cheapest round-trip flights first.

Deals found on 1/3

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 5, 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 5, 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
4,248 reviews

Crew

8.6

Entertainment

7.5

Food

7.0

Comfort

8.0

Boarding

8.1

Overall

8.0

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
4,248 reviews
Southwest
8.0
Very good
4,248 reviews

Crew

8.6

Entertainment

7.5

Food

7.0

Comfort

8.0

Boarding

8.1

Overall

8.0

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
8,017 reviews
Southwest
8.0
Very good
4,248 reviews

Crew

8.6

Entertainment

7.5

Food

7.0

Comfort

8.0

Boarding

8.1

Overall

8.0

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
9,138 reviews
Southwest
8.0
Very good
4,248 reviews

Crew

8.6

Entertainment

7.5

Food

7.0

Comfort

8.0

Boarding

8.1

Overall

8.0

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
11,079 reviews
Southwest
8.0
Very good
4,248 reviews

Crew

8.6

Entertainment

7.5

Food

7.0

Comfort

8.0

Boarding

8.1

Overall

8.0

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
3,064 reviews
Southwest
8.0
Very good
4,248 reviews

Crew

8.6

Entertainment

7.5

Food

7.0

Comfort

8.0

Boarding

8.1

Overall

8.0

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 $309, Frontier can have you in Illinois from Ontario in 7h 52m. The distance between Ontario and Illinois is about 1557 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 $373, our data shows the cheapest flight currently is $148. When looking at the most popular route, (Ontario - Chicago O'Hare Intl), you can expect to pay $178 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

See prices for flight routes from nearby airports that may be better suited for you.
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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 5, 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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