How long is the flight from Ontario to Illinois?

For as low as $379, Frontier can have you in Illinois from Ontario in 5h 29m. 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?

$71 is the cheapest one-way deal found within the past few days, from Frontier. You may also be able to find cheap deals on Delta and Alaska Airlines, with prices starting from $145 and $159, respectively.

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.

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).

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 $660, our data shows the cheapest flight currently is $175. When looking at the most popular route, (Ontario - Chicago O'Hare Intl), you can expect to pay $130 for that flight.

What are the most popular airlines that fly from Ontario to Illinois?

Consider United Airlines, Southwest or American Airlines when booking your flight. These represent the most popular airlines when flying from Ontario to Illinois.

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.

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.

$63+ Cheap Flights from Ontario to Illinois

Q: How much does it cost to fly round-trip from Ontario to Illinois?

Airfare is below average for this route at the moment. Ontario to Illinois flights typically cost between $389 and $528 in December. The cheapest round-trip price found within the last 3 days was $162 on Frontier (Dec 4-Dec 10).

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Enter your travel information like dates, passengers, trip type (one-way or round trip), and preferred cabin class then click “Find deals”

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Cheap flight deals from Ontario to Illinois

Most accurate provider	Justfly.com 3 stars
Most trusted provider	Justfly.com 3 stars
Round-trip from	$130 (CheapOair)
One-way from	$63 (Trip.com)
Popular in	December
Cheapest in	September
Average price	$303
Good round-trip deal	$336 or less
Good one-way deal	$218 or less

Provider with most accurate pricing for Los Angeles-Chicago (CHI) flight deals.

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Provider most trusted by Cheapflights users for Los Angeles-Chicago (CHI) flights.

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From Ontario to Illinois

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One-way flight from Ontario to Illinois

Search Deals

Highest demand for flights based on searches. 9% potential increase in price ($29 potential increase over avg. RT price).

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Cheapest flight prices on average. 1% potential price decrease ($5 potential savings vs. average RT price).

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Average for round-trip flights in October 2025

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Price to beat on a round-trip flight from Ontario to Illinois.

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Price to beat on a one-way flight from Ontario to Illinois.

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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 October 28, 2025.

Tue 11/188:45 amONT - STL

1 stop22h 22mFrontier

Thu 11/209:54 pmSTL - ONT

1 stop18h 32mFrontier

Deal found 10/26

$130

Wed 11/1912:58 amONT - STL

1 stop16h 00mFrontier

Thu 11/209:54 pmSTL - ONT

1 stop18h 32mFrontier

Deal found 10/26

$131

Sat 11/88:00 amONT - STL

1 stop5h 56mFrontier

Tue 11/117:45 pmSTL - ONT

1 stop27h 44mFrontier

Deal found 10/26

$150

Fri 12/53:20 pmONT - STL

1 stop16h 54mFrontier

Sat 12/67:43 pmSTL - ONT

1 stop21h 23mFrontier

Deal found 10/26

$154

Thu 12/42:59 pmONT - ORD

1 stop18h 43mFrontier

Wed 12/104:01 pmORD - ONT

2 stops28h 34mFrontier

Deal found 10/26

$162

Fri 12/123:20 pmONT - STL

1 stop16h 54mFrontier

Mon 1/125:44 pmSTL - ONT

1 stop22h 49mFrontier

Deal found 10/26

$163

Wed 11/128:45 amONT - ORD

2 stops23h 16mMultiple Airlines

Sat 11/157:15 amORD - ONT

1 stop18h 35mMultiple Airlines

Deal found 10/26

$164

Fri 12/56:19 pmONT - ORD

1 stop19h 28mMultiple Airlines

Wed 12/104:01 pmORD - ONT

2 stops28h 34mMultiple Airlines

Deal found 10/26

$165

Sat 11/1512:05 pmONT - ORD

1 stop9h 24mFrontier

Tue 11/186:05 pmORD - ONT

1 stop29h 22mFrontier

Deal found 10/27

$166

Sat 11/86:53 amONT - ORD

1 stop14h 36mMultiple Airlines

Wed 11/121:48 pmORD - ONT

2 stops23h 22mMultiple Airlines

Deal found 10/26

$167

Mon 12/82:59 pmONT - ORD

1 stop6h 58mFrontier

Mon 12/157:00 amORD - ONT

1 stop9h 25mFrontier

Deal found 10/26

$170

Thu 12/186:45 amONT - STL

1 stop25h 17mFrontier

Mon 1/125:44 pmSTL - ONT

1 stop22h 49mFrontier

Deal found 10/26

$172

Best flights from Ontario to Illinois
Discover carefully curated flight deals from Ontario to Illinois that have cost, travel time, and layovers in mind to ensure you get the best travel experience. Data last updated October 28, 2025.

Mon 11/106:00 amONT - STL

1 stop5h 57mFrontier

Mon 11/172:42 pmSTL - ONT

1 stop9h 15mFrontier

Deal found 10/27

$176

Thu 12/42:59 pmONT - PIA

2 stops27h 22mMultiple Airlines

Wed 12/107:23 pmPIA - ONT

1 stop27h 54mMultiple Airlines

Deal found 10/27

$234

Wed 12/1710:25 pmONT - STL

1 stop7h 59mDelta

Sun 1/185:00 pmSTL - ONT

1 stop6h 48mDelta

Deal found 10/26

$316

Wed 2/186:00 amONT - ORD

1 stop9h 50mAlaska Airlines

Tue 2/242:00 pmORD - ONT

1 stop10h 37mAlaska Airlines

Deal found 10/28

$318

Sat 11/88:00 amONT - STL

1 stop5h 56mFrontier

Tue 11/117:45 pmSTL - ONT

1 stop27h 44mFrontier

Deal found 10/27

$176

Sat 2/211:45 pmONT - MLI

1 stop5h 29mUnited Airlines

Tue 2/248:49 amMLI - ONT

1 stop5h 54mUnited Airlines

Deal found 10/25

$379

Sat 2/2112:26 pmONT - MLI

2 stops8h 42mAmerican Airlines

Tue 2/2411:07 amMLI - ONT

1 stop9h 33mAmerican Airlines

Deal found 10/26

$384

Sat 11/1512:05 pmONT - STL

1 stop19h 02mFrontier

Sun 11/162:42 pmSTL - ONT

1 stop18h 35mFrontier

Deal found 10/27

$182

Wed 12/36:30 amONT - MDW

Nonstop3h 45mSouthwest

Mon 12/88:15 amMDW - ONT

Nonstop4h 20mSouthwest

Deal found 10/26

$405

Sat 11/812:05 pmONT - STL

1 stop19h 02mMultiple Airlines

Sun 11/166:21 pmSTL - ONT

2 stops26h 28mMultiple Airlines

Deal found 10/27

$288

Wed 11/128:45 amONT - STL

2 stops30h 42mFrontier

Sat 11/157:45 pmSTL - ONT

1 stop17h 25mFrontier

Deal found 10/27

$257

Tue 12/1610:25 pmONT - STL

1 stop7h 59mDelta

Sat 1/175:00 pmSTL - ONT

1 stop6h 48mDelta

Deal found 10/26

$316

Wed 2/186:55 pmONT - ORD

1 stop8h 09mAlaska Airlines

Fri 2/202:05 pmORD - ONT

1 stop7h 42mAlaska Airlines

Deal found 10/27

$340

Wed 12/174:49 pmONT - STL

1 stop6h 12mDelta

Sat 1/176:00 amSTL - ONT

1 stop7h 54mDelta

Deal found 10/26

$316

Sat 12/612:13 pmONT - ORD

1 stop9h 46mAlaska Airlines

Wed 12/102:05 pmORD - ONT

2 stops23h 14mAlaska Airlines

Deal found 10/28

$346

Tue 11/251:29 pmONT - PIA

1 stop5h 27mUnited Airlines

Thu 11/2710:51 amPIA - ONT

1 stop6h 30mUnited Airlines

Deal found 10/27

$383

Wed 4/156:43 amONT - PIA

1 stop5h 33mAmerican Airlines

Sat 4/1811:31 amPIA - ONT

2 stops8h 15mAmerican Airlines

Deal found 10/25

$384

Sun 11/2312:58 amONT - STL

1 stop7h 04mFrontier

Tue 11/257:57 pmSTL - ONT

1 stop6h 00mFrontier

Deal found 10/27

$303

Tue 12/95:45 amONT - MDW

1 stop8h 10mSouthwest

Tue 12/305:20 amMDW - ONT

1 stop7h 20mSouthwest

Deal found 10/28

$425

Tue 1/277:00 amONT - ORD

2 stops14h 55mAlaska Airlines

Sat 1/318:00 amORD - ONT

2 stops11h 05mAlaska Airlines

Deal found 10/25

$353

Thu 12/47:30 pmONT - PIA

2 stops12h 51mAmerican Airlines

Wed 12/1011:30 amPIA - ONT

2 stops8h 49mAmerican Airlines

Deal found 10/27

$391

Mon 11/246:30 amONT - STL

1 stop12h 39mFrontier

Wed 11/269:54 pmSTL - ONT

1 stop18h 32mFrontier

Deal found 10/27

$303

Wed 11/267:00 amONT - PIA

1 stop7h 40mUnited Airlines

Thu 11/2710:51 amPIA - ONT

1 stop6h 30mUnited Airlines

Deal found 10/28

$404

Sat 4/2512:00 pmONT - BMI

1 stop8h 23mDelta

Wed 4/293:50 pmBMI - ONT

1 stop8h 19mDelta

Deal found 10/25

$379

Sat 12/610:50 amONT - MDW

Nonstop3h 45mSouthwest

Wed 12/108:45 amMDW - ONT

2 stops8h 35mSouthwest

Deal found 10/26

$430

Wed 4/157:00 amONT - PIA

1 stop7h 31mUnited Airlines

Sat 4/185:20 pmPIA - ONT

1 stop7h 06mUnited Airlines

Deal found 10/25

$404

Thu 2/57:56 pmONT - ORD

2 stops19h 14mAlaska Airlines

Sun 2/88:00 amORD - ONT

1 stop9h 08mAlaska Airlines

Deal found 10/26

$368

Fri 10/3110:43 pmONT - STL

1 stop15h 13mFrontier

Mon 11/39:07 pmSTL - ONT

1 stop25h 35mFrontier

Deal found 10/27

$319

Fri 11/711:36 amONT - MLI

1 stop8h 44mDelta

Mon 11/105:12 pmMLI - ONT

1 stop7h 52mDelta

Deal found 10/26

$394

Sun 12/147:10 amONT - ORD

1 stop27h 59mAlaska Airlines

Sun 1/188:00 amORD - ONT

2 stops11h 05mAlaska Airlines

Deal found 10/27

$368

Last-minute flights from Ontario to Illinois
Discover last-minute flight deals from Ontario to Illinois. Data last updated October 28, 2025 and is based on user searches.

Thu 11/61:46 pmONT - MDW

1 stop20h 51mFrontier

Thu 11/139:39 pmMDW - ONT

1 stop11h 50mFrontier

Deal found 10/28

$176

Sat 11/88:00 amONT - STL

1 stop5h 56mFrontier

Tue 11/117:45 pmSTL - ONT

1 stop27h 44mFrontier

Deal found 10/26

$150

Sat 11/86:53 amONT - ORD

1 stop14h 36mMultiple Airlines

Wed 11/121:48 pmORD - ONT

2 stops23h 22mMultiple Airlines

Deal found 10/26

$167

Sat 11/812:05 pmONT - ORD

1 stop9h 24mFrontier

Wed 11/126:05 pmORD - ONT

1 stop19h 05mFrontier

Deal found 10/27

$176

Tue 11/118:45 amONT - ORD

2 stops24h 45mMultiple Airlines

Sat 11/156:25 pmORD - ONT

1 stop14h 02mMultiple Airlines

Deal found 10/26

$177

Tue 11/118:45 amONT - STL

1 stop22h 22mFrontier

Sun 11/162:42 pmSTL - ONT

1 stop18h 35mFrontier

Deal found 10/28

$182

Wed 11/128:45 amONT - ORD

2 stops23h 16mMultiple Airlines

Sat 11/157:15 amORD - ONT

1 stop18h 35mMultiple Airlines

Deal found 10/26

$164

Wed 11/128:45 amONT - MDW

1 stop24h 45mFrontier

Sun 11/166:30 amMDW - ONT

1 stop14h 19mFrontier

Deal found 10/27

$182

Thu 11/131:46 pmONT - ORD

1 stop7h 58mFrontier

Mon 11/176:00 amORD - ONT

2 stops19h 50mFrontier

Deal found 10/26

$178

Sat 11/1512:05 pmONT - ORD

1 stop9h 24mFrontier

Tue 11/186:05 pmORD - ONT

1 stop29h 22mFrontier

Deal found 10/27

$166

Tue 11/188:45 amONT - STL

1 stop22h 22mFrontier

Thu 11/209:54 pmSTL - ONT

1 stop18h 32mFrontier

Deal found 10/26

$130

Wed 11/1912:58 amONT - STL

1 stop16h 00mFrontier

Thu 11/209:54 pmSTL - ONT

1 stop18h 32mFrontier

Deal found 10/26

$131

One-way flights from Ontario to Illinois
Search for one-way flight options from Ontario to Illinois. Find affordable one-way fares based on user searches. Data last updated October 28, 2025.

Thu 1/226:00 amONT - STL

1 stop26h 02mFrontier

Deal found 10/27

$63

Thu 1/86:00 amONT - MDW

1 stop12h 02mFrontier

Deal found 10/26

$63

Thu 1/86:00 amONT - ORD

1 stop10h 53mFrontier

Deal found 10/26

$63

Mon 11/177:54 amONT - MDW

1 stop7h 07mFrontier

Deal found 10/27

$65

Mon 11/171:46 pmONT - ORD

1 stop7h 58mFrontier

Deal found 10/28

$65

Tue 11/188:45 amONT - ORD

1 stop8h 53mFrontier

Deal found 10/28

$66

Thu 2/266:56 pmONT - MDW

1 stop16h 08mFrontier

Deal found 10/27

$67

Sat 11/1512:05 pmONT - ORD

1 stop9h 24mFrontier

Deal found 10/26

$68

Wed 12/36:15 amONT - STL

1 stop27h 57mFrontier

Deal found 10/26

$71

Sat 11/1512:05 pmONT - MDW

1 stop21h 25mFrontier

Deal found 10/26

$71

Tue 11/118:45 amONT - ORD

1 stop28h 54mFrontier

Deal found 10/26

$71

Mon 11/176:00 amONT - STL

1 stop12h 12mFrontier

Deal found 10/27

$75

Fly from

Fly to

Route

Depart

Return

Price

OntarioSt. Louis

ONT - STL

ONTSTL

Ontario

Mon 11/10

6:00 am-1:57 pm

1 stop5h 57m

Lambert-St Louis

Mon 11/17

2:42 pm-9:57 pm

1 stop9h 15m

$176

OntarioSt. Louis

ONT - STL

ONTSTL

Ontario

Sat 11/8

8:00 am-3:56 pm

1 stop5h 56m

Lambert-St Louis

Tue 11/11

7:45 pm-9:29 pm

1 stop27h 44m

$176

OntarioSt. Louis

ONT - STL

ONTSTL

Ontario

Sat 11/15

12:05 pm-9:07 am

1 stop19h 02m

Lambert-St Louis

Sun 11/16

2:42 pm-7:17 am

1 stop18h 35m

$182

OntarioPeoria

ONT - PIA

ONTPIA

Ontario

Thu 12/4

2:59 pm-8:21 pm

2 stops27h 22m

Greater Peoria

Wed 12/10

7:23 pm-9:17 pm

1 stop27h 54m

$234

OntarioSt. Louis

ONT - STL

ONTSTL

Ontario

Wed 11/12

8:45 am-5:27 pm

2 stops30h 42m

Lambert-St Louis

Sat 11/15

7:45 pm-11:10 am

1 stop17h 25m

$257

OntarioSt. Louis

ONT - STL

ONTSTL

Ontario

Sat 11/8

12:05 pm-9:07 am

1 stop19h 02m

Lambert-St Louis

Sun 11/16

6:21 pm-6:49 pm

2 stops26h 28m

$288

OntarioSt. Louis

ONT - STL

ONTSTL

Ontario

Sun 11/23

12:58 am-10:02 am

1 stop7h 04m

Lambert-St Louis

Tue 11/25

7:57 pm-11:57 pm

1 stop6h 00m

$303

OntarioSt. Louis

ONT - STL

ONTSTL

Ontario

Mon 11/24

6:30 am-9:09 pm

1 stop12h 39m

Lambert-St Louis

Wed 11/26

9:54 pm-2:26 pm

1 stop18h 32m

$303

OntarioSt. Louis

ONT - STL

ONTSTL

Ontario

Wed 12/17

10:25 pm-8:24 am

1 stop7h 59m

Lambert-St Louis

Sun 1/18

5:00 pm-9:48 pm

1 stop6h 48m

$316

OntarioSt. Louis

ONT - STL

ONTSTL

Ontario

Tue 12/16

10:25 pm-8:24 am

1 stop7h 59m

Lambert-St Louis

Sat 1/17

5:00 pm-9:48 pm

1 stop6h 48m

$316

Flights are sorted by cheapest round-trip flights first.

Deals found on 10/27

Showing 1-10 of 60 results

...

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 July is currently the most expensive (average of $138). 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?

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?

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.

How much does it cost to fly round-trip from Ontario to Illinois?

Reviews of airlines servicing Illinois

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

4,240 reviews

Reviews

1 / 20

8.0

Excellent

Walter,Aug 2025

OAK - SAN

Dozens of flights and I've never seen a row's beverages forgotten. I even went back and asked the attendant to check on them and nothing. I really hope it didn't have something to do with the Black mother with her kid in the row. Otherwise it was a typical Southwest flight, rapid boarding, tolerable leg room.

Southwest

8.0

Very good

4,240 reviews

Southwest

8.0

Very good

4,240 reviews

Reviews

1 / 20

8.0

Excellent

Walter,Aug 2025

OAK - SAN

Delta

7.9

Good

7,994 reviews

Southwest

8.0

Very good

4,240 reviews

Reviews

1 / 20

8.0

Excellent

Walter,Aug 2025

OAK - SAN

United Airlines

7.4

Good

9,001 reviews

Southwest

8.0

Very good

4,240 reviews

Reviews

1 / 20

8.0

Excellent

Walter,Aug 2025

OAK - SAN

American Airlines

7.2

Good

11,032 reviews

Southwest

8.0

Very good

4,240 reviews

Reviews

1 / 20

8.0

Excellent

Walter,Aug 2025

OAK - SAN

Frontier

5.8

Fair

3,124 reviews

Southwest

8.0

Very good

4,240 reviews

Reviews

1 / 20

8.0

Excellent

Walter,Aug 2025

OAK - SAN

Related info for your journey

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 $379, Frontier can have you in Illinois from Ontario in 5h 29m. 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?
$71 is the cheapest one-way deal found within the past few days, from Frontier. You may also be able to find cheap deals on Delta and Alaska Airlines, with prices starting from $145 and $159, 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 $660, our data shows the cheapest flight currently is $175. When looking at the most popular route, (Ontario - Chicago O'Hare Intl), you can expect to pay $130 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 July is currently the most expensive (average of $138). 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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Complete your trip

Illinois car rentals

Chicago O'Hare Intl Airport car rentals

Chicago Midway Airport car rentals

Moline Quad-City Airport car rentals

Greater Peoria Airport car rentals

Bloomington-Normal Airport car rentals

Chicago Greater Rockford Airport car rentals

Springfield Capital Airport car rentals

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Belleville Airport car rentals

Marion Williamson County Airport car rentals

Quincy Regional Airport car rentals

Top 5 airlines flying from Ontario to Illinois

Airline	Cheapest	Average	Flexibility	On-time
Frontier	Cheapest$110	Average$217	FlexibilityNo cancel fee	On-time62%
United Airlines	Cheapest$227	Average$463	FlexibilityNo cancel fee	On-time69%
Southwest	Cheapest$237	Average$423	FlexibilityNo cancel fee	On-time63%
American Airlines	Cheapest$246	Average$485	FlexibilityNo cancel fee	On-time71%
Delta	Cheapest$256	Average$383	FlexibilityNo cancel fee	On-timeN/A

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$63+ 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 1/22. Fares are subject to change and may not be available on all flights or dates of travel.

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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 October 28, 2025.

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Find flight deals from Ontario to Illinois

Cheapest flights from Ontario to IllinoisExplore 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 October 28, 2025.

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 October 28, 2025.

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Use the filters below to find and compare flights from Ontario to Illinois that are best for you.

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.

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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?

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 October 28, 2025.

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.

How much does it cost to fly round-trip from Ontario to Illinois?

Reviews of airlines servicing Illinois

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.

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?

How long is the flight from Ontario to Illinois?

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

What are the most popular routes from Ontario to Illinois?

What are the cheapest flights from Ontario to Illinois?

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

How can I find direct flights from Ontario to Illinois?

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

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

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Alternative routes for Ontario to Illinois

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Top 5 airlines flying from Ontario to Illinois

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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 October 28, 2025.