HomeSearch by dateVacation packagesHotelsFlight dealsCar rentalTravel tips & news
Illinois

$38+ 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 3/18. Fares are subject to change and may not be available on all flights or dates of travel.
ONT — ORD
Feb 25 — Mar 41
Tue 2/25
Tue 3/4
1 adult, Economy
We work with more than 300 partners to bring you better travel deals

Find cheap flights from Ontario to Illinois with Cheapflights

1. Tell us where you want to go
Enter your travel information like dates, passengers, trip type (one-way or round trip), and preferred cabin class then click “Find deals”
2. Select your favorite providers
We find the providers serving your travel needs. Choose up to four travel providers to compare side-by-side for flights, hotels, or car rentals.
3. Compare prices and book
Review each provider’s pricing and select the best option for you! Book through your favorite provider’s website for a seamless experience.

Cheap flight deals from Ontario to Illinois

Keep the following information in mind while searching for Ontario to Illinois flight deals. Data was last updated February 20, 2025.

Most accurate provider

FlightHub
3 stars

Most trusted provider

FlightHub
3 stars

Round-trip from

$125
(Frontier)

One-way from

$38
(Trip.com)

Popular in

March

Cheapest in

October

Average price

$274

Good round-trip deal

$269 or less

Good one-way deal

$158 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. 2% potential increase in price ($6 potential increase over avg. RT price).
Search Deals
Cheapest flight prices on average. 1% potential price decrease ($6 potential savings vs. average RT price).
Search Deals
Average for round-trip flights in February 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

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 February 20, 2025.

This Frontier deal was found by Cheapflights users on 2/20. 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.
Sun 4/1312:59 amONT - STL
1 stop6h 07mFrontier
Sat 4/196:51 pmSTL - ONT
1 stop7h 08mFrontier
Deal found 2/20$125
This Booking.com deal was found by Cheapflights users on 2/19. 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.
Fri 3/712:59 amONT - MDW
1 stop21h 18mFrontier
Tue 3/117:50 amMDW - ONT
1 stop12h 09mFrontier
Deal found 2/19$135
This Booking.com deal was found by Cheapflights users on 2/19. 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.
Fri 3/712:59 amONT - ORD
1 stop10h 21mFrontier
Tue 3/116:45 amORD - ONT
1 stop19h 19mFrontier
Deal found 2/19$135
This United Airlines deal was found by Cheapflights users on 2/18. 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.
Sat 6/217:00 amONT - ORD
Nonstop3h 58mUnited Airlines
Tue 6/248:20 pmORD - ONT
Nonstop4h 31mUnited Airlines
Deal found 2/18$227
This Expedia deal was found by Cheapflights users on 2/19. 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.
Tue 5/611:46 amONT - ORD
1 stop10h 13mMultiple Airlines
Thu 5/87:00 amORD - ONT
1 stop12h 47mMultiple Airlines
Deal found 2/19$229
This American Airlines deal was found by Cheapflights users on 2/19. 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.
Tue 5/612:46 pmONT - ORD
1 stop6h 23mAmerican Airlines
Sat 5/107:00 amORD - ONT
1 stop6h 54mAmerican Airlines
Deal found 2/19$247
This Southwest deal was found by Cheapflights users on 2/19. 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.
Fri 4/253:15 pmONT - MDW
1 stop7h 15mSouthwest
Mon 4/287:05 pmMDW - ONT
1 stop5h 55mSouthwest
Deal found 2/19$252
This Delta deal was found by Cheapflights users on 2/20. 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 4/2210:15 pmONT - MDW
1 stop8h 52mDelta
Tue 4/2912:48 pmMDW - ONT
1 stop8h 40mDelta
Deal found 2/20$257
This Delta deal was found by Cheapflights users on 2/20. 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 4/235:15 pmONT - ORD
1 stop5h 38mDelta
Mon 4/287:50 amORD - ONT
1 stop8h 05mDelta
Deal found 2/20$257
This American Airlines deal was found by Cheapflights users on 2/20. 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.
Sat 5/310:54 amONT - MLI
1 stop8h 29mAmerican Airlines
Sat 5/103:25 pmMLI - ONT
1 stop8h 34mAmerican Airlines
Deal found 2/20$289
This American Airlines deal was found by Cheapflights users on 2/20. 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.
Wed 4/29:47 amONT - PIA
2 stops10h 08mAmerican Airlines
Sat 4/56:33 amPIA - ONT
1 stop9h 16mAmerican Airlines
Deal found 2/20$294
This Alaska Airlines deal was found by Cheapflights users on 2/19. 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.
Thu 10/3011:30 amONT - ORD
1 stop10h 29mAlaska Airlines
Thu 11/610:00 amORD - ONT
1 stop10h 17mAlaska Airlines
Deal found 2/19$303

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 February 20, 2025.

Fly from

Ontario

Fly to

Illinois

Route

Depart

Return

Price

OntarioSt. Louis

ONT - STL

ONTSTL

Ontario

Sun 4/13

12:59 am-9:06 am

1 stop6h 07m

Lambert-St Louis

Sat 4/19

6:51 pm-11:59 pm

1 stop7h 08m

$125

OntarioChicago

ONT - MDW

ONTMDW

Ontario

Fri 3/7

12:59 am-12:17 am

1 stop21h 18m

Chicago Midway

Tue 3/11

7:50 am-5:59 pm

1 stop12h 09m

$135

OntarioChicago

ONT - ORD

ONTORD

Ontario

Fri 3/7

12:59 am-1:20 pm

1 stop10h 21m

Chicago O'Hare Intl

Tue 3/11

6:45 am-12:04 am

1 stop19h 19m

$135

OntarioChicago

ONT - ORD

ONTORD

Ontario

Thu 4/24

6:24 pm-6:05 am

1 stop9h 41m

Chicago O'Hare Intl

Mon 4/28

11:41 am-5:24 pm

1 stop7h 43m

$224

OntarioChicago

ONT - ORD

ONTORD

Ontario

Sat 6/21

7:00 am-12:58 pm

Nonstop3h 58m

Chicago O'Hare Intl

Tue 6/24

8:20 pm-10:51 pm

Nonstop4h 31m

$227

OntarioChicago

ONT - ORD

ONTORD

Ontario

Wed 3/26

7:35 pm-5:08 am

1 stop7h 33m

Chicago O'Hare Intl

Sun 3/30

5:00 am-10:07 am

1 stop7h 07m

$247

OntarioChicago

ONT - MDW

ONTMDW

Ontario

Fri 4/25

3:15 pm-12:30 am

1 stop7h 15m

Chicago Midway

Mon 4/28

7:05 pm-11:00 pm

1 stop5h 55m

$252

OntarioChicago

ONT - MDW

ONTMDW

Ontario

Tue 4/22

10:15 pm-9:07 am

1 stop8h 52m

Chicago Midway

Tue 4/29

12:48 pm-7:28 pm

1 stop8h 40m

$257

OntarioChicago

ONT - ORD

ONTORD

Ontario

Wed 4/23

5:15 pm-12:53 am

1 stop5h 38m

Chicago O'Hare Intl

Mon 4/28

7:50 am-1:55 pm

1 stop8h 05m

$257

OntarioMoline

ONT - MLI

ONTMLI

Ontario

Sat 5/3

10:54 am-9:23 pm

1 stop8h 29m

Moline Quad-City

Sat 5/10

3:25 pm-9:59 pm

1 stop8h 34m

$289

Flights are sorted by cheapest round-trip flights first.

Deals found on 2/18

Showing 1-10 of 54 results
1
2
3
...
6

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 $321). 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 February 20, 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 February 20, 2025.
Get a feel of what it's like to fly with Southwest, Alaska Airlines and Delta 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
4,411 reviews

Entertainment

7.6

Overall

8.1

Food

7.1

Crew

8.7

Boarding

8.2

Comfort

8.1

Reviews

1 / 20

2.0
Mediocre

Anonymous,Feb 2025

MCO - STL

Cancelled at last minute, SWA unable to assist in formulating alternate plans. Wound up renting a car and driving 13 hours to beat bad weather forecast at home. Not SWA’s fault that there was significant bad weather across the country.

Southwest
8.1
Very good
4,411 reviews
Southwest
8.1
Very good
4,411 reviews

Entertainment

7.6

Overall

8.1

Food

7.1

Crew

8.7

Boarding

8.2

Comfort

8.1

Reviews

1 / 20

2.0
Mediocre

Anonymous,Feb 2025

MCO - STL

Cancelled at last minute, SWA unable to assist in formulating alternate plans. Wound up renting a car and driving 13 hours to beat bad weather forecast at home. Not SWA’s fault that there was significant bad weather across the country.

Alaska Airlines
8.0
Very good
9,692 reviews
Southwest
8.1
Very good
4,411 reviews

Entertainment

7.6

Overall

8.1

Food

7.1

Crew

8.7

Boarding

8.2

Comfort

8.1

Reviews

1 / 20

2.0
Mediocre

Anonymous,Feb 2025

MCO - STL

Cancelled at last minute, SWA unable to assist in formulating alternate plans. Wound up renting a car and driving 13 hours to beat bad weather forecast at home. Not SWA’s fault that there was significant bad weather across the country.

Delta
8.0
Very good
8,220 reviews
Southwest
8.1
Very good
4,411 reviews

Entertainment

7.6

Overall

8.1

Food

7.1

Crew

8.7

Boarding

8.2

Comfort

8.1

Reviews

1 / 20

2.0
Mediocre

Anonymous,Feb 2025

MCO - STL

Cancelled at last minute, SWA unable to assist in formulating alternate plans. Wound up renting a car and driving 13 hours to beat bad weather forecast at home. Not SWA’s fault that there was significant bad weather across the country.

Hawaiian Airlines
7.9
Good
2,317 reviews
Southwest
8.1
Very good
4,411 reviews

Entertainment

7.6

Overall

8.1

Food

7.1

Crew

8.7

Boarding

8.2

Comfort

8.1

Reviews

1 / 20

2.0
Mediocre

Anonymous,Feb 2025

MCO - STL

Cancelled at last minute, SWA unable to assist in formulating alternate plans. Wound up renting a car and driving 13 hours to beat bad weather forecast at home. Not SWA’s fault that there was significant bad weather across the country.

JetBlue
7.4
Good
3,070 reviews
Southwest
8.1
Very good
4,411 reviews

Entertainment

7.6

Overall

8.1

Food

7.1

Crew

8.7

Boarding

8.2

Comfort

8.1

Reviews

1 / 20

2.0
Mediocre

Anonymous,Feb 2025

MCO - STL

Cancelled at last minute, SWA unable to assist in formulating alternate plans. Wound up renting a car and driving 13 hours to beat bad weather forecast at home. Not SWA’s fault that there was significant bad weather across the country.

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?

    $38 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 Delta, with prices starting from $114 and $129, 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 $245, our data shows the cheapest flight currently is $113. When looking at the most popular route, (Ontario - Chicago O'Hare Intl), you can expect to pay $125 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, 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 $321). 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

Browse thousands of different options on Cheapflights for your next trip

Toggle through the tabs below to find thousands of options on Cheapflights for your next trip.

Alternative routes for Ontario to Illinois

See prices for flight routes from nearby airports that may be better suited for you.
Los Angeles to John F Kennedy Intl flights
Los Angeles to Newark flights
San Francisco to John F Kennedy Intl flights
Los Angeles to Seattle flights
San Francisco to Newark flights
San Francisco to Seattle flights
San Francisco to Las Vegas flights
Los Angeles to Miami flights
Los Angeles to LaGuardia flights
Los Angeles to Dallas/Fort Worth flights
Los Angeles to O'Hare Intl flights
Los Angeles to Honolulu flights
San Jose to Las Vegas flights
San Francisco to Los Angeles flights
Los Angeles to Orlando flights
Los Angeles to Las Vegas flights
Santa Ana to Las Vegas flights
Los Angeles to Fort Lauderdale flights
Oakland to Las Vegas flights
Burbank to Las Vegas flights
Oakland to Los Angeles flights
Los Angeles to Sky Harbor Intl flights
Los Angeles to San Francisco flights
San Francisco to Honolulu flights
Los Angeles to Reagan-National flights
San Francisco to O'Hare Intl flights
Los Angeles to Dulles Intl flights
Los Angeles to Boston flights
San Jose to Los Angeles flights
San Francisco to Ontario flights
San Francisco to LaGuardia flights
Burbank to Dallas/Fort Worth flights
Burbank to Newark flights
Los Angeles to Hobby flights
Los Angeles to Baltimore flights
Los Angeles to Oakland flights
Los Angeles to Austin flights
San Diego to Seattle flights
Ontario to Seattle flights
Los Angeles to Nashville flights
Santa Ana to Dallas/Fort Worth flights
Santa Ana to Newark flights
Los Angeles to San Jose flights
San Francisco to Dulles Intl flights
Los Angeles to Portland flights
Los Angeles to New Orleans flights
San Francisco to Sky Harbor Intl flights
San Francisco to Dallas/Fort Worth flights
San Francisco to Miami flights
Ontario to Honolulu flights

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 February 20, 2025.
AirlineCheapestAverageFlexibilityOn-time
Spirit AirlinesCheapest$74Average$177FlexibilityNo cancel feeOn-time65%
FrontierCheapest$109Average$212FlexibilityNo cancel feeOn-time62%
Alaska AirlinesCheapest$161Average$438FlexibilityNo cancel feeOn-time75%
DeltaCheapest$236Average$395FlexibilityNo cancel feeOn-timeN/A
United AirlinesCheapest$246Average$516FlexibilityNo cancel feeOn-time69%
American AirlinesCheapest$246Average$503FlexibilityNo cancel feeOn-time71%
SouthwestCheapest$307Average$488FlexibilityNo cancel feeOn-time63%
100% Free
Cheapflights is completely free to use, so you can start saving the moment you arrive.
Book with Flexibility
Our users can plan ahead with confidence and find flights with no change fees
Travel Smart
Millions of people come to us for their flight needs every year. We help make travel planning easy by providing useful insights and data-driven graphs that can inform your decisions.