How many flights depart from Ontario to Illinois on average per week?

4 flights are operational weekly from Ontario to Illinois as of December 2025. The most popular departure day for this route is Mon, with 25% of flights per week taking off on this day.

What is the cheapest airline that flies from Ontario to Illinois?

Frontier, Alaska Airlines, and United Airlines are the most popular carriers operating from Ontario to Illinois

What airlines fly to Illinois?

American Airlines, United Airlines and Spirit Airlines are the top three most popular airlines that fly to Illinois from Ontario according to our data. American Airlines is the first choice among our users, with 45% of people opting to fly with this airline when traveling to Illinois. Keep in mind that there are 8 different airlines that fly to Illinois on a routine basis, so you have a few additional options to choose from.

When did momondo last update prices for flights from Ontario Airport to Illinois?

Prices for flights from Ontario Airport to Illinois were last updated today.

How many operators does momondo search for flights from Ontario Airport to Illinois?

As of December 2025, there are 5 operators available to choose from for flights from Ontario Airport to Illinois.

How old do you have to be to fly from Ontario Airport to Illinois?

The minimum age for a child to fly alone is five, but airlines offering an unaccompanied minor (UNMR) service may have their age restrictions, such as regulations concerning flight duration, timing, and layovers. It is recommended that you verify with the airline you are booking with for travel from Ontario Airport to Illinois.

What documentation or ID do you need to fly to Illinois?

The travel and health documents required for your trip to Illinois can vary based on your itinerary and personal situation. As a rule, consider having multiple documents such as a national ID card or driver’s license, and a passport valid for six-months after you plan to arrive at Illinois. We always recommend checking with your airline or a trusted third party such as IATA to get advice.

$70 Cheap Flights from Ontario to Illinois in 2025/26

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Find the cheapest flights from Ontario to Illinois

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Cheap round-trip flights

Enter your travel dates to find the best prices.

11:04 am - 9:06 pm

ONT

STL

8h 02m1 stop

3:46 pm - 11:24 pm

STL

ONT

9h 38m1 stop

$141Frontier

Thu, Jan 29 - Sat, Jan 31

7:15 am - 2:46 pm

ONT

STL

5h 31m1 stop

5:44 pm - 9:17 pm

STL

ONT

5h 33m1 stop

$148Frontier

Sat, Jan 31 - Mon, Mar 2

6:00 am - 11:14 pm

ONT

ORD

15h 14m1 stop

3:33 pm - 9:34 pm

ORD

ONT

32h 01m2 stops

$193Multiple Airlines

Thu, Feb 19 - Mon, Feb 23

11:04 am - 8:36 pm

ONT

MLI

7h 32m1 stop

9:26 pm - 9:23 am

MLI

ONT

13h 57m1 stop

$243Multiple Airlines

Thu, Jan 29 - Thu, Feb 5

12:41 pm - 10:33 pm

ONT

MLI

7h 52m1 stop

5:51 am - 11:31 am

MLI

ONT

7h 40m1 stop

$309Delta

Tue, Jan 27 - Sun, Feb 8

7:16 am - 3:27 pm

ONT

MLI

6h 11m1 stop

3:58 pm - 10:48 pm

MLI

ONT

8h 50m1 stop

$329American Airlines

Thu, Jan 8 - Wed, Jan 14

9:59 am - 9:58 pm

ONT

MLI

9h 59m2 stops

3:58 pm - 10:48 pm

MLI

ONT

8h 50m1 stop

$334American Airlines

Thu, Jan 8 - Wed, Jan 14

12:41 pm - 10:33 pm

ONT

MLI

7h 52m1 stop

5:51 am - 11:31 am

MLI

ONT

7h 40m1 stop

$359Delta

Fri, Jan 30 - Tue, Feb 10

7:00 am - 4:45 pm

ONT

PIA

7h 45m1 stop

5:25 pm - 10:26 pm

PIA

ONT

7h 01m1 stop

$379United Airlines

Wed, Apr 15 - Fri, Apr 24

1:24 pm - 8:34 pm

ONT

MLI

5h 10m1 stop

10:47 am - 9:58 pm

MLI

ONT

13h 11m2 stops

$384United Airlines

Tue, Feb 3 - Sat, Feb 7

Frontier flights from Ontario to Illinois

Our best Frontier deals on Ontario to Illinois flight tickets

Frontier

Jan 29

ONT11:04 amOntario

8h 02m

1 stop

STL9:06 pmLambert-St Louis

Jan 31

STL3:46 pmLambert-St Louis

9h 38m

1 stop

ONT11:24 pmOntario

$141

Find similar

Frontier

Jan 22

ONT6:20 amOntario

10h 11m

1 stop

ORD6:31 pmChicago O'Hare Intl

Jan 25

ORD9:38 pmChicago O'Hare Intl

19h 03m

1 stop

ONT2:41 pmOntario

$148

Find similar

Frontier

Jan 22

ONT3:22 pmOntario

27h 07m

1 stop

ORD8:29 pmChicago O'Hare Intl

Jan 25

ORD9:38 pmChicago O'Hare Intl

16h 32m

1 stop

ONT12:10 pmOntario

$149

Find similar

Alaska Airlines flights from Ontario to Illinois

Our best Alaska Airlines deals on Ontario to Illinois flight tickets

Alaska Airlines

Feb 14

ONT6:14 amOntario

30h 09m

1 stop

STL2:23 pmLambert-St Louis

Feb 24

STL7:00 amLambert-St Louis

30h 08m

1 stop

ONT11:08 amOntario

$322

Find similar

Alaska Airlines

Feb 17

ONT6:14 amOntario

29h 37m

1 stop

STL1:51 pmLambert-St Louis

Feb 23

STL2:47 pmLambert-St Louis

22h 21m

1 stop

ONT11:08 amOntario

$354

Find similar

Fly from

Fly to

Route

Depart

Return

Price

OntarioSt. Louis

ONT - STL

ONTSTL

Ontario

Thu 1/29

11:04 am-9:06 pm

1 stop8h 02m

Lambert-St Louis

Sat 1/31

3:46 pm-11:24 pm

1 stop9h 38m

$141

OntarioSt. Louis

ONT - STL

ONTSTL

Ontario

Sat 1/31

7:15 am-2:46 pm

1 stop5h 31m

Lambert-St Louis

Mon 3/2

5:44 pm-9:17 pm

1 stop5h 33m

$148

OntarioChicago

ONT - ORD

ONTORD

Ontario

Thu 2/19

6:00 am-11:14 pm

1 stop15h 14m

Chicago O'Hare Intl

Mon 2/23

3:33 pm-9:34 pm

2 stops32h 01m

$193

OntarioMoline

ONT - MLI

ONTMLI

Ontario

Thu 1/29

11:04 am-8:36 pm

1 stop7h 32m

Moline Quad-City

Thu 2/5

9:26 pm-9:23 am

1 stop13h 57m

$243

OntarioMoline

ONT - MLI

ONTMLI

Ontario

Tue 1/27

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

OntarioMoline

ONT - MLI

ONTMLI

Ontario

Thu 1/8

7:16 am-3:27 pm

1 stop6h 11m

Moline Quad-City

Wed 1/14

3:58 pm-10:48 pm

1 stop8h 50m

$329

OntarioMoline

ONT - MLI

ONTMLI

Ontario

Thu 1/8

9:59 am-9:58 pm

2 stops9h 59m

Moline Quad-City

Wed 1/14

3:58 pm-10:48 pm

1 stop8h 50m

$334

OntarioMoline

ONT - MLI

ONTMLI

Ontario

Fri 1/30

12:41 pm-10:33 pm

1 stop7h 52m

Moline Quad-City

Tue 2/10

5:51 am-11:31 am

1 stop7h 40m

$359

OntarioPeoria

ONT - PIA

ONTPIA

Ontario

Wed 4/15

7:00 am-4:45 pm

1 stop7h 45m

Greater Peoria

Fri 4/24

5:25 pm-10:26 pm

1 stop7h 01m

$379

OntarioMoline

ONT - MLI

ONTMLI

Ontario

Tue 2/3

1:24 pm-8:34 pm

1 stop5h 10m

Moline Quad-City

Sat 2/7

10:47 am-9:58 pm

2 stops13h 11m

$384

Flights are sorted by cheapest round-trip flights first.

Showing 1-10 of 20 resultsSorted by cheapest first

How to get the cheapest flight ticket from Ontario to Illinois

Look no further. We've gone through all the searches for this route on momondo so you have the important information and insights to find the cheapest flight ticket for your trip

Prices

Airlines

Other information

What is the cheapest month to fly to Illinois?

The cheapest month to fly to Illinois from Ontario is in June. Flight prices, which tend to average around $317, are often lower during this time because this is during the off-season. If you aren’t able to travel to Illinois during the month of June, then flying in September is also cheap. Prices for this month can be found on momondo for an average of $317.

What is the cheapest day to depart on your flight to Illinois?

The cheapest day to depart from Ontario to Illinois is on a Thursday when prices can be found for as low as $441. Flights from Ontario to Illinois on a Sunday will generally be more expensive and average around $502. Keep in mind that these prices on both days could fluctuate depending on the season and the demand.

What is the cheapest time of day to depart on your flight to Illinois?

Our most recent data shows that the best time of day to fly to Illinois is in the afternoon. Flights from Ontario to Illinois during this time can be as low as $276. Flights in the evening are often more expensive with an average ticket price of $551.

What is the cheapest Ontario to Illinois flight route?

Fly from Ontario to Chicago Midway for the best Ontario - Illinois flight prices

How far in advance should I book a flight to Illinois?

You are more likely to see cheaper flights to Illinois from Ontario when booking weeks ahead of your departure date. In general, you can expect to find flights to Illinois for around $390 when searching weeks out. However, flight prices might be lower outside of this timeframe. For example, people recently found flights to Illinois from Ontario for as low as $293 on momondo.

What cabin class options are available on Ontario to Illinois flights?

There are 4 cabin classes available to choose from on Ontario to Illinois flights. Cabin price and availability will vary by airline so perform a search above to find the right deals for you.

Can stopping save me money on Ontario to Illinois flights?

You could potentially save up to 16% on your flight if you consider stops on a Ontario to Illinois flight.

Cheap Ontario to Illinois flight deals and tips

Find info about flight duration, direct flights, and airports for your flight from Ontario to Illinois

Best Price Found	$183
Fastest flight time	3h 45m
Direct flights	Every day
Airports in Illinois	98 airports

The best one-way flight to Illinois from Ontario in the past 72 hours is $183. The best round-trip flight deal from Ontario to Illinois found on momondo in the last 72 hours is $376.

The fastest flight from Ontario to Illinois takes 3h 45m

Direct flights go from Ontario to Illinois every day.

There are 98 airports in Illinois. From Ontario there are direct flights to Chicago O'Hare Intl (ORD), Chicago Midway (MDW).

Search flight deals

When did momondo last update prices for flights from Ontario Airport to Illinois?
Prices for flights from Ontario Airport to Illinois were last updated today.
How many operators does momondo search for flights from Ontario Airport to Illinois?
As of December 2025, there are 5 operators available to choose from for flights from Ontario Airport to Illinois.
How old do you have to be to fly from Ontario Airport to Illinois?
The minimum age for a child to fly alone is five, but airlines offering an unaccompanied minor (UNMR) service may have their age restrictions, such as regulations concerning flight duration, timing, and layovers. It is recommended that you verify with the airline you are booking with for travel from Ontario Airport to Illinois.
What documentation or ID do you need to fly to Illinois?
The travel and health documents required for your trip to Illinois can vary based on your itinerary and personal situation. As a rule, consider having multiple documents such as a national ID card or driver’s license, and a passport valid for six-months after you plan to arrive at Illinois. We always recommend checking with your airline or a trusted third party such as IATA to get advice.
What is the most popular plane model from Ontario to Illinois?
momondo data reveals that the most frequently booked plane model on the route from Ontario to Illinois is Airbus A321neo, representing 18.30% of all bookings. The subsequent popular models are Boeing 737-800 at 14.88%, Boeing 737 MAX 8 at 11.90%, and Airbus A318/A319/A320/A321 at 5.95%.

Best airlines flying from Ontario to Illinois

Compare and see reviews for airlines that fly from Ontario to Illinois with momondo

Airline	Rating	Free Cancellation	Price
Frontier	PriceFrom $110	Free Cancellation	Rating 5.8 3,084 reviews	Search Frontier flights
United Airlines	PriceFrom $227	Free Cancellation	Rating 7.4 9,095 reviews	Search United Airlines flights
Southwest	PriceFrom $237	Free Cancellation	Rating 7.9 4,253 reviews	Search Southwest flights
American Airlines	PriceFrom $246	Free Cancellation	Rating 7.2 11,050 reviews	Search American Airlines flights
Delta	PriceFrom $256	Free Cancellation	Rating 7.9 8,008 reviews	Search Delta flights

Why use momondo?

Why should I use momondo to find a flight deal from Ontario to Illinois?

momondo collates all your flight options in one place and lets you filter them to find the perfect flight from Ontario to Illinois. momondo saves you time and could save you money on your trip.

Can I find flights from Ontario to Illinois with flexible booking policies on momondo?

Flights from Ontario to Illinois with flexible booking policies can be found by using the search form above and then selecting our dedicated flexible booking filter, which will highlight only the flights where this policy is applied.

How can momondo help me find flights from Ontario to Illinois?

Once you have performed a search for Ontario to Illinois flights, momondo helps you find the right one by offering useful filters to narrow down your flight selection. Flights can be filtered by multiple factors such as airline, airport and price; but also by other criteria like aircraft type and payment method.

I’m not ready to book a flight from Ontario to Illinois right now. Can momondo alert me if prices change?

If you are simply researching potential flights to Illinois, momondo offers a useful price alert feature which will track prices for flights to Illinois from Ontario and alert you when they change.

An easier way to manage your Illinois trip

We make it super easy to schedule, organize and travel with friends or family. Trips is free — and available to use no matter where you book.

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Find better results for your trip to Illinois

Popular cities in Illinois

Flights to New Yorkfrom $34

Flights to Los Angelesfrom $49

Flights to Miamifrom $49

Flights to Chicagofrom $49

Flights to Orlandofrom $41

Flights to San Franciscofrom $53

Flights to Las Vegasfrom $40

Flights to Washington, D.C.from $49

Flights to Bostonfrom $55

Flights to Atlantafrom $49

Flights to Dallasfrom $52

Flights to Seattlefrom $58

Cheap flights from Ontario to Illinois from $70

This is the cheapest one-way flight price found by a momondo user in the last 72 hours by searching for a flight from Ontario to Illinois departing on 2/6. Fares may change, and may not be available for all flights or travel dates. Click the price to refresh the search for this deal.

Big names and deals

Big names and deals

Filter for what you want

Filter for what you want

Trusted and free

Trusted and free

Price Alerts

Price Alerts

Find the cheapest flights from Ontario to Illinois

Cheap round-trip flights

Cheap one-way flights

Cheap last minute flights

Cheap direct flights

Frontier flights from Ontario to Illinois

Our best Frontier deals on Ontario to Illinois flight tickets

Alaska Airlines flights from Ontario to Illinois

Our best Alaska Airlines deals on Ontario to Illinois flight tickets

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

See travel insights to Illinois from

How to get the cheapest flight ticket from Ontario to Illinois

What is the cheapest month to fly to Illinois?

What is the cheapest day to depart on your flight to Illinois?

What is the cheapest time of day to depart on your flight to Illinois?

Our most recent data shows that the best time of day to fly to Illinois is in the afternoon. Flights from Ontario to Illinois during this time can be as low as $276. Flights in the evening are often more expensive with an average ticket price of $551.

What is the cheapest Ontario to Illinois flight route?

Fly from Ontario to Chicago Midway for the best Ontario - Illinois flight prices

How far in advance should I book a flight to Illinois?

What cabin class options are available on Ontario to Illinois flights?

There are 4 cabin classes available to choose from on Ontario to Illinois flights. Cabin price and availability will vary by airline so perform a search above to find the right deals for you.

Can stopping save me money on Ontario to Illinois flights?

You could potentially save up to 16% on your flight if you consider stops on a Ontario to Illinois flight.

What is the cheapest airline that flies from Ontario to Illinois?

Frontier, Alaska Airlines, and United Airlines are the most popular carriers operating from Ontario to Illinois

What airlines fly to Illinois?

How many flights depart from Ontario to Illinois on average per week?

4 flights are operational weekly from Ontario to Illinois as of December 2025. The most popular departure day for this route is Mon, with 25% of flights per week taking off on this day.

Cheap Ontario to Illinois flight deals and tips

Find info about flight duration, direct flights, and airports for your flight from Ontario to Illinois

Best Price Found

Fastest flight time

Direct flights

Airports in Illinois

When did momondo last update prices for flights from Ontario Airport to Illinois?

How many operators does momondo search for flights from Ontario Airport to Illinois?

How old do you have to be to fly from Ontario Airport to Illinois?

What documentation or ID do you need to fly to Illinois?

What is the most popular plane model from Ontario to Illinois?

Best airlines flying from Ontario to Illinois

Compare and see reviews for airlines that fly from Ontario to Illinois with momondo

Why use momondo?

Why should I use momondo to find a flight deal from Ontario to Illinois?

Can I find flights from Ontario to Illinois with flexible booking policies on momondo?

How can momondo help me find flights from Ontario to Illinois?

I’m not ready to book a flight from Ontario to Illinois right now. Can momondo alert me if prices change?

An easier way to manage your Illinois trip

We make it super easy to schedule, organize and travel with friends or family. Trips is free — and available to use no matter where you book.

Get notified when prices go down

Daily price changes in your inbox - only with Price Alerts.

Find better results for your trip to Illinois

Popular cities in Illinois

Popular flights according to clicks in the last 7 days on momondo