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$73+ Cheap flights from Illinois to Ontario (ONT)

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 3/25. Fares are subject to change and may not be available on all flights or dates of travel.
ORD — ONT
mrt. 14 — mrt. 211
za 3/14
za 3/21
1 adult, Economy
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Cheap flight deals from Illinois to Ontario

Cheapest flights from Illinois to Ontario
Explore the most affordable flight options available from Illinois to Ontario. Find the lowest fares from popular airlines and budget airlines, with prices last updated on februari 12, 2026.

This Kiwi.com deal was found by Cheapflights users on 2/8. 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 Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
do 4/308:12 pm
STL
-
ONT
1 stop13h 19m
Frontier
vr 5/112:59 am
ONT
-
STL
1 stop16h 13m
Frontier
Deal found 2/8$160
This Kiwi.com deal was found by Cheapflights users on 2/8. 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 Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
di 3/104:28 pm
ORD
-
ONT
2 stops33h 31m
Frontier
di 3/172:23 pm
ONT
-
ORD
1 stop13h 45m
Frontier
Deal found 2/8$160
This Kiwi.com deal was found by Cheapflights users on 2/10. 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 Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
wo 4/229:18 pm
ORD
-
ONT
1 stop12h 46m
Frontier
za 4/2512:59 am
ONT
-
ORD
1 stop6h 51m
Frontier
Deal found 2/10$170
This Kiwi.com deal was found by Cheapflights users on 2/10. 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 Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
do 3/54:16 pm
ORD
-
ONT
1 stop9h 43m
Frontier
wo 3/186:15 am
ONT
-
ORD
1 stop25h 28m
Frontier
Deal found 2/10$172
This Kiwi.com deal was found by Cheapflights users on 2/9. 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.
wo 3/114:28 pm
ORD
-
ONT
2 stops22h 43m
Frontier
di 3/172:23 pm
ONT
-
ORD
1 stop13h 45m
Frontier
Deal found 2/9$173
This Kiwi.com deal was found by Cheapflights users on 2/9. 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.
wo 4/299:18 pm
ORD
-
ONT
1 stop12h 46m
Multiple Airlines
za 5/27:18 pm
ONT
-
ORD
1 stop8h 13m
Multiple Airlines
Deal found 2/9$174
This Kiwi.com deal was found by Cheapflights users on 2/9. 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.
di 5/59:18 pm
ORD
-
ONT
1 stop18h 22m
Frontier
zo 5/108:26 am
ONT
-
ORD
1 stop25h 51m
Frontier
Deal found 2/9$175
This Kiwi.com deal was found by Cheapflights users on 2/9. 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.
wo 4/299:18 pm
ORD
-
ONT
1 stop12h 46m
Frontier
do 4/3012:59 am
ONT
-
ORD
1 stop6h 51m
Frontier
Deal found 2/9$177
This Kiwi.com deal was found by Cheapflights users on 2/9. 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.
di 3/178:06 pm
STL
-
ONT
1 stop19h 22m
Frontier
vr 4/175:33 pm
ONT
-
STL
1 stop23h 39m
Frontier
Deal found 2/9$179
This Kiwi.com deal was found by Cheapflights users on 2/10. 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 Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
wo 3/48:30 am
ORD
-
ONT
2 stops15h 04m
Frontier
wo 3/186:15 am
ONT
-
ORD
1 stop25h 28m
Frontier
Deal found 2/10$180
This Kiwi.com deal was found by Cheapflights users on 2/9. 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.
di 3/37:23 pm
ORD
-
ONT
2 stops28h 11m
Multiple Airlines
ma 3/910:57 am
ONT
-
ORD
1 stop17h 11m
Multiple Airlines
Deal found 2/9$181
This Kiwi.com deal was found by Cheapflights users on 2/11. 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 Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
vr 4/102:29 pm
ORD
-
ONT
1 stop11h 27m
Frontier
ma 4/139:02 pm
ONT
-
ORD
1 stop7h 45m
Frontier
Deal found 2/11$184

Find flight deals from Illinois to Ontario

Keep the following information in mind while searching for Illinois to Ontario flight deals. Data was last updated februari 12, 2026.

Most accurate provider

FlightHub
3 stars

Most trusted provider

FlightHub
3 stars

Round-trip from

$160
(Kiwi.com)

One-way from

$73
(Trip.com)

Popular in

December

Cheapest in

September

Average price

$347

Good round-trip deal

$436 or less

Good one-way deal

$154 or less
Provider with most accurate pricing for Chicago (CHI)-Los Angeles flight deals.
Search Deals
Provider most trusted by Cheapflights users for Chicago (CHI)-Los Angeles flights.
Search Deals
From Illinois to Ontario
Search Deals
One-way flight from Illinois to Ontario
Search Deals
Highest demand for flights based on searches. 15% potential increase in price ($54 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 February 2026
Search Deals
Price to beat on a round-trip flight from Illinois to Ontario.
Search Deals
Price to beat on a one-way flight from Illinois to Ontario.
Search Deals

Cheapflights Fare Finder

 
Customize your flight search to find flights from Illinois to Ontario 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 februari 12, 2026.
Use the filters below to find and compare flights from Illinois to Ontario that are best for you.

Fly from

Illinois

Fly to

Ontario

Route

Depart

Return

Price

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

di 3/10

8:06 pm-9:03 pm

1 stop26h 57m

Ontario

di 3/17

6:15 am-9:49 am

1 stop25h 34m

$193

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

do 4/30

11:21 am-11:24 pm

2 stops14h 03m

Ontario

vr 5/1

12:59 am-7:12 pm

1 stop16h 13m

$218

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

ma 2/23

1:54 pm-11:59 pm

1 stop12h 05m

Ontario

wo 2/25

8:40 am-3:53 pm

1 stop5h 13m

$232

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

vr 3/20

8:12 pm-11:59 pm

1 stop5h 47m

Ontario

ma 3/23

11:17 am-11:19 am

1 stop22h 02m

$252

ChicagoOntario

ORD - ONT

ORDONT

Chicago O'Hare Intl

za 3/7

7:00 am-3:08 pm

1 stop10h 08m

Ontario

za 3/14

12:02 pm-11:56 pm

1 stop9h 54m

$283

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

di 3/17

7:15 am-12:23 pm

1 stop7h 08m

Ontario

wo 3/18

5:09 pm-12:21 am

1 stop5h 12m

$287

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

di 3/17

6:00 am-11:47 am

1 stop7h 47m

Ontario

di 3/17

5:09 pm-12:21 am

1 stop5h 12m

$287

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

za 3/7

7:00 am-12:07 pm

1 stop7h 07m

Ontario

za 3/14

1:20 pm-9:31 pm

1 stop6h 11m

$305

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

wo 3/11

6:00 am-11:47 am

1 stop7h 47m

Ontario

di 3/17

6:00 am-1:31 pm

1 stop5h 31m

$305

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

za 3/7

7:00 am-12:07 pm

1 stop7h 07m

Ontario

wo 3/18

5:09 pm-12:21 am

1 stop5h 12m

$305

Flights are sorted by cheapest round-trip flights first.

Deals found on 2/11

Showing 1-10 of 60 results
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Best time to book a flight from Illinois to Ontario

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

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

Currently, September is the cheapest month in which you can book a flight from Illinois to Ontario (average of $80). Flying from Illinois to Ontario in January is currently the most expensive (average of $159). 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 IL to ONT?

Find hourly flight availability from Illinois to Ontario. Discover flight options and departure times throughout the day, allowing you to choose a departure time that suits your schedule. Data last updated februari 12, 2026.

It’s typically best to fly out from Illinois to Ontario at noon. Doing so could potentially save you 27% on the flight price compared to flying in the afternoon, which is usually more expensive.

Related info for your journey

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

    Located just 3.1 mi from the city center, Ontario (ONT) is the airport most travelers will use when flying to Ontario from Illinois.

  • How long is the flight from Illinois to Ontario?

    For as low as $287, Frontier can have you in Ontario from Illinois in 7h 08m. The distance between Illinois and Ontario is about 1541 mi. This flight may include one or multiple stops.

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

    $75 is the cheapest one-way deal found within the past few days, from Frontier. You may also be able to find cheap deals on American Airlines and Delta, with prices starting from $92 and $110, respectively.

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

    When deciding which route to take from Illinois to Ontario consider Chicago O'Hare Intl - Ontario, Lambert-St Louis - Ontario or Chicago Midway - Ontario as they are the most popular.

  • What are the cheapest flights from Illinois to Ontario?

    The cheapest flight price from Illinois to Ontario is $395. On average you can expect to pay $542. The most popular route, (Chicago O'Hare Intl - Ontario), can usually be booked for $160.

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

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

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

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

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

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

    Currently, September is the cheapest month in which you can book a flight from Illinois to Ontario (average of $80). Flying from Illinois to Ontario in January is currently the most expensive (average of $159). 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 Illinois to Ontario

See prices for flight routes from nearby airports that may be better suited for you.
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Top 5 airlines flying from Illinois to Ontario

Discover the top 5 airlines that operate flights from Illinois to Ontario. 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 februari 12, 2026.
AirlineCheapestAverageFlexibilityOn-time
FrontierCheapest$123Average$208FlexibilityNo cancel feeOn-time62%
American AirlinesCheapest$231Average$488FlexibilityNo cancel feeOn-time71%
United AirlinesCheapest$237Average$467FlexibilityNo cancel feeOn-time69%
SouthwestCheapest$246Average$465FlexibilityNo cancel feeOn-time63%
DeltaCheapest$256Average$256FlexibilityNo cancel feeOn-timeN/A

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