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$70+ 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 2/6. Fares are subject to change and may not be available on all flights or dates of travel.
ONT — ORD
jan 10 — jan 171
sáb 1/10
sáb 1/17
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 dezembro 11, 2025.

This CheapOair deal was found by Cheapflights users on 12/10. 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.
sáb 12/276:00 amONT - STL
1 stop13h 25mFrontier
sáb 1/37:43 pmSTL - ONT
1 stop6h 16mFrontier
Deal found 12/10$185
This Mytrip deal was found by Cheapflights users on 12/8. 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.
ter 12/306:17 pmONT - STL
1 stop20h 07mFrontier
seg 1/510:10 pmSTL - ONT
1 stop18h 59mFrontier
Deal found 12/8$194
This Booking.com deal was found by Cheapflights users on 12/10. 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.
qua 12/246:20 pmONT - ORD
1 stop23h 01mFrontier
qui 1/810:32 pmORD - ONT
1 stop18h 22mFrontier
Deal found 12/10$194
This Expedia deal was found by Cheapflights users on 12/10. 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.
seg 12/296:00 pmONT - STL
1 stop25h 25mFrontier
seg 1/127:43 pmSTL - ONT
1 stop6h 13mFrontier
Deal found 12/10$203
This CheapOair deal was found by Cheapflights users on 12/10. 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.
seg 12/296:00 pmONT - STL
1 stop25h 25mFrontier
qui 1/15:19 pmSTL - ONT
1 stop5h 58mFrontier
Deal found 12/10$205
This Frontier deal was found by Cheapflights users on 12/9. 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.
qui 12/256:00 amONT - ORD
1 stop6h 17mFrontier
qui 1/810:32 pmORD - ONT
1 stop11h 04mFrontier
Deal found 12/9$207
This Frontier deal was found by Cheapflights users on 12/11. 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.
qui 12/256:00 amONT - STL
1 stop8h 24mFrontier
qui 1/15:19 pmSTL - ONT
1 stop5h 58mFrontier
Deal found 12/11$208
This CheapOair deal was found by Cheapflights users on 12/9. 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.
sáb 12/205:16 pmONT - ORD
1 stop26h 23mFrontier
qui 1/1510:41 pmORD - ONT
1 stop21h 03mFrontier
Deal found 12/9$208
This CheapOair deal was found by Cheapflights users on 12/10. 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.
qui 12/256:00 amONT - ORD
1 stop6h 17mFrontier
dom 1/410:49 pmORD - ONT
1 stop20h 26mFrontier
Deal found 12/10$209
This Kiwi.com deal was found by Cheapflights users on 12/9. 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.
qua 12/316:45 amONT - ORD
1 stop15h 27mFrontier
dom 1/410:49 pmORD - ONT
1 stop20h 26mFrontier
Deal found 12/9$214
This Kiwi.com deal was found by Cheapflights users on 12/9. 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.
qua 12/246:00 pmONT - ORD
1 stop18h 17mFrontier
dom 1/410:49 pmORD - ONT
1 stop20h 26mFrontier
Deal found 12/9$218
This Kiwi.com deal was found by Cheapflights users on 12/9. 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.
ter 12/306:17 pmONT - ORD
2 stops27h 55mFrontier
dom 1/410:49 pmORD - ONT
1 stop24h 28mFrontier
Deal found 12/9$219

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 dezembro 11, 2025.

Most accurate provider

Justfly.com
3 stars

Most trusted provider

Justfly.com
3 stars

Round-trip from

$141
(Kiwi.com)

One-way from

$70
(Trip.com)

Popular in

December

Cheapest in

September

Average price

$367

Good round-trip deal

$376 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 ($7 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 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 dezembro 11, 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

qua 2/4

7:15 am-2:46 pm

1 stop5h 31m

Lambert-St Louis

sáb 2/28

7:43 pm-11:59 pm

1 stop6h 16m

$166

OntarioSt. Louis

ONT - STL

ONTSTL

Ontario

qui 1/8

10:18 pm-12:12 pm

1 stop11h 54m

Lambert-St Louis

seg 1/12

7:43 pm-11:56 pm

1 stop6h 13m

$182

OntarioSt. Louis

ONT - STL

ONTSTL

Ontario

ter 1/20

3:07 pm-2:46 pm

2 stops21h 39m

Lambert-St Louis

sex 1/23

7:39 pm-11:24 pm

1 stop29h 45m

$185

OntarioSt. Louis

ONT - STL

ONTSTL

Ontario

qui 1/8

10:18 pm-12:12 pm

1 stop11h 54m

Lambert-St Louis

sex 1/9

10:16 pm-2:26 pm

1 stop18h 10m

$193

OntarioSt. Louis

ONT - STL

ONTSTL

Ontario

sex 1/9

6:00 am-10:02 am

1 stop26h 02m

Lambert-St Louis

seg 1/12

7:43 pm-11:56 pm

1 stop6h 13m

$225

OntarioSt. Louis

ONT - STL

ONTSTL

Ontario

qua 12/31

6:00 am-4:24 pm

1 stop8h 24m

Lambert-St Louis

dom 1/4

10:10 pm-9:17 pm

1 stop25h 07m

$229

OntarioSt. Louis

ONT - STL

ONTSTL

Ontario

seg 1/19

6:10 am-6:51 pm

1 stop10h 41m

Lambert-St Louis

dom 1/25

9:27 pm-7:10 pm

1 stop23h 43m

$259

OntarioChicago

ONT - ORD

ONTORD

Ontario

qua 1/7

7:30 am-11:53 pm

1 stop14h 23m

Chicago O'Hare Intl

dom 1/11

7:30 am-1:56 pm

1 stop8h 26m

$285

OntarioChicago

ONT - ORD

ONTORD

Ontario

ter 3/3

4:02 pm-11:56 pm

1 stop29h 54m

Chicago O'Hare Intl

sex 3/6

7:00 am-11:32 pm

1 stop18h 32m

$304

OntarioChicago

ONT - ORD

ONTORD

Ontario

dom 2/8

6:00 am-5:10 pm

1 stop9h 10m

Chicago O'Hare Intl

ter 2/10

8:00 am-8:36 pm

1 stop14h 36m

$304

Flights are sorted by cheapest round-trip flights first.

Deals found on 12/9

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 dezembro 11, 2025.

Unlike in the morning, when flights are generally more expensive, you can save up to 42% on flights from Ontario to Illinois by exploring options for tickets in the afternoon.

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

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

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

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 dezembro 11, 2025.
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
7.9
Good
4,252 reviews

Overall

7.9

Boarding

8.1

Crew

8.6

Comfort

8.0

Food

7.0

Entertainment

7.5

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
7.9
Good
4,252 reviews
Southwest
7.9
Good
4,252 reviews

Overall

7.9

Boarding

8.1

Crew

8.6

Comfort

8.0

Food

7.0

Entertainment

7.5

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
8,008 reviews
Southwest
7.9
Good
4,252 reviews

Overall

7.9

Boarding

8.1

Crew

8.6

Comfort

8.0

Food

7.0

Entertainment

7.5

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
9,094 reviews
Southwest
7.9
Good
4,252 reviews

Overall

7.9

Boarding

8.1

Crew

8.6

Comfort

8.0

Food

7.0

Entertainment

7.5

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
11,048 reviews
Southwest
7.9
Good
4,252 reviews

Overall

7.9

Boarding

8.1

Crew

8.6

Comfort

8.0

Food

7.0

Entertainment

7.5

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
5.8
Fair
3,084 reviews
Southwest
7.9
Good
4,252 reviews

Overall

7.9

Boarding

8.1

Crew

8.6

Comfort

8.0

Food

7.0

Entertainment

7.5

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 $166, Frontier can have you in Illinois from Ontario in 5h 31m. 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 $449, our data shows the cheapest flight currently is $141. When looking at the most popular route, (Ontario - Chicago O'Hare Intl), you can expect to pay $148 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 dezembro 11, 2025.
AirlineCheapestAverageFlexibilityOn-time
FrontierCheapest$110Average$225FlexibilityNo cancel feeOn-time62%
United AirlinesCheapest$227Average$465FlexibilityNo cancel feeOn-time69%
SouthwestCheapest$237Average$418FlexibilityNo cancel feeOn-time63%
American AirlinesCheapest$246Average$471FlexibilityNo cancel feeOn-time71%
DeltaCheapest$256Average$355FlexibilityNo cancel feeOn-timeN/A

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