What are the cheapest airlines flying from St. Louis to Ontario round-trip?

Frontier, at $188, was found to be the cheapest airline from St. Louis to Ontario.Alternate airlines to your destination round-trip include Delta and Hawaiian Airlines. Frontier is priced at 47% lower than the current average price of a flight leaving 3 months from now.

What are the cheapest airlines to fly from St. Louis to Ontario one-way?

The cheapest airline one-way is Frontier, with whom users have recently found tickets for as low as $87. However, be on the lookout for offers from Delta and American Airlines, as they are both options that can get you from St. Louis to Ontario for a low price.

What are the most popular airlines that fly from St. Louis to Ontario?

Before booking your flight from St. Louis to Ontario check out the most popular airlines for this route: American Airlines, Delta or Frontier.

What is the cheapest day to fly round-trip from St. Louis to Ontario?

Saturday flights are generally found to be more expensive for flights from St. Louis to Ontario. This shouldn’t discourage you from searching, as you can still find great deals by being flexible with your options. Use our search form to find deals on tickets to Ontario.

How far in advance should I book a flight from St. Louis to Ontario?

Travelers have found it’s best to book a flight 51 days in advance to save up to 57% compared to booking the same week of travel. As your travel date approaches, the cost of this flight route may potentially increase. While opting to book 51 days out may not be an option for all, there are still additional ways to secure a deal in the near future. You might find a flight from St. Louis to Ontario 1-2 weeks in advance for as low as $347, or $639 for flights within the next 24 hours.

What is the cheapest month to fly from St. Louis to Ontario?

Our data shows that September tends to be the cheapest month to fly to Ontario from St. Louis. Users have commonly found prices around $392 for the month, but tickets can be as low as $151. Due to multiple factors, prepare for potentially higher prices in March.

Most accurate provider : When it comes to deals on St. Louis-Ontario flights, users find the pricing of Mytrip to be most consistent on Cheapflights vs. Mytrip Users can find the same prices on St. Louis-Ontario flight deals on Cheapflights vs. Mytrip >95% of the time. Price accuracy is based on data collected from St. Louis-Ontario flight searches over the past month and is updated monthly.

Most trusted provider : When it comes to deals on St. Louis-Ontario flights, Cheapflights users trust Mytrip the most. Mytrip has received a user feedback score of 3 out of 3 stars (3 being the best), meaning they have been trusted the most by Cheapflights users looking for St. Louis-Ontario flight deals. Provider user feedback score is based on Cheapflights searches over the past month and is updated monthly.

Can I find deals for flights from St. Louis to Ontario that include hotel bookings?

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

How can I find direct flights from St. Louis to Ontario?

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

Can I find deals for business class flights from St. Louis to Ontario?

Yes. Cheapflights offers flight deals from St. Louis 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.

$87+ Flights from St. Louis to Ontario

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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”

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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.

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Cheapflights Tip: The best prices from Lambert-St Louis to Ontario are usually found in February or June, booked 68 days in advance, depart on a Tuesday or Wednesday and return on a Monday

Cheap flight deals from St. Louis to Ontario

Most accurate provider	Mytrip 3 stars
Most trusted provider	Mytrip 3 stars
Round-trip from	$188 (CheapOair)
One-way from	$87 (Cheapflightsfares)
Popular in	March
Cheapest in	February
Average price	$362

Provider with most accurate pricing for Lambert-St Louis-Ontario flight deals.

Search Deals

Provider most trusted by Cheapflights users for Lambert-St Louis-Ontario flights.

Search Deals

From Lambert-St Louis to Ontario

Search Deals

One-way flight from Lambert-St Louis to Ontario

Search Deals

Highest demand for flights based on searches. 3% potential increase in price ($13 potential increase over avg. RT price).

Search Deals

Cheapest flight prices on average. 5% potential price decrease ($21 potential savings vs. average RT price).

Search Deals

Average for round-trip flights in May 2025

Search Deals

Find flight deals from St. Louis to Ontario

Cheapest flights from St. Louis to Ontario
Explore the most affordable flight options available from St. Louis to Ontario. Find the lowest fares from popular airlines and budget airlines, with prices last updated on May 1, 2025.

Sun 5/49:55 pmSTL - ONT

1 stop11h 29mFrontier

Tue 5/612:59 amONT - STL

1 stop7h 00mFrontier

Deal found 4/30

$178

Wed 7/235:23 pmSTL - ONT

1 stop7h 04mDelta

Tue 7/297:05 amONT - STL

1 stop7h 13mDelta

Deal found 4/30

$307

Fri 5/96:53 pmSTL - ONT

1 stop7h 06mMultiple Airlines

Sun 5/1112:16 pmONT - STL

3 stops29h 54mMultiple Airlines

Deal found 4/30

$319

Wed 9/103:35 pmSTL - ONT

1 stop10h 24mHawaiian Airlines

Mon 9/1511:39 amONT - STL

1 stop10h 20mHawaiian Airlines

Deal found 4/29

$324

Sat 6/73:08 pmSTL - ONT

2 stops8h 30mAmerican Airlines

Wed 6/1112:55 pmONT - STL

2 stops8h 05mAmerican Airlines

Deal found 4/30

$359

Thu 11/610:00 amSTL - ONT

2 stops8h 00mSouthwest

Tue 11/116:40 amONT - STL

1 stop8h 25mSouthwest

Deal found 4/30

$367

Wed 9/103:35 pmSTL - ONT

1 stop10h 24mAlaska Airlines

Mon 9/157:10 amONT - STL

2 stops14h 49mAlaska Airlines

Deal found 4/29

$385

Tue 7/225:00 amSTL - ONT

2 stops9h 32mUnited Airlines

Wed 7/301:34 pmONT - STL

1 stop6h 16mUnited Airlines

Deal found 4/29

$402

Best flights from St. Louis to Ontario
Discover carefully curated flight deals from St. Louis to Ontario that have cost, travel time, and layovers in mind to ensure you get the best travel experience. Data last updated May 1, 2025.

Mon 5/129:55 pmSTL - ONT

1 stop16h 13mFrontier

Sun 5/1812:59 amONT - STL

1 stop6h 10mFrontier

Deal found 4/30

$188

Wed 7/233:42 pmSTL - ONT

1 stop8h 45mDelta

Wed 7/3010:05 pmONT - STL

1 stop8h 21mDelta

Deal found 4/30

$307

Wed 9/103:35 pmSTL - ONT

1 stop10h 24mHawaiian Airlines

Mon 9/1511:39 amONT - STL

1 stop10h 20mHawaiian Airlines

Deal found 4/29

$324

Sat 6/73:08 pmSTL - ONT

2 stops8h 30mAmerican Airlines

Wed 6/1112:55 pmONT - STL

2 stops8h 05mAmerican Airlines

Deal found 4/30

$359

Mon 5/126:00 amSTL - ONT

2 stops11h 32mMultiple Airlines

Sun 5/1812:59 amONT - STL

1 stop6h 10mMultiple Airlines

Deal found 4/30

$368

Wed 9/103:35 pmSTL - ONT

1 stop10h 24mAlaska Airlines

Mon 9/157:10 amONT - STL

2 stops14h 49mAlaska Airlines

Deal found 4/29

$385

Tue 7/221:42 pmSTL - ONT

2 stops11h 10mUnited Airlines

Tue 7/295:05 amONT - STL

1 stop5h 41mUnited Airlines

Deal found 4/29

$402

Fri 5/233:00 pmSTL - ONT

2 stops8h 10mSouthwest

Sun 5/257:00 amONT - STL

2 stops9h 10mSouthwest

Deal found 4/30

$465

Last-minute flights from St. Louis to Ontario
Discover last-minute flight deals from St. Louis to Ontario. Data last updated May 1, 2025 and is based on user searches.

Sun 5/49:55 pmSTL - ONT

1 stop11h 29mFrontier

Tue 5/612:59 amONT - STL

1 stop7h 00mFrontier

Deal found 4/30

$178

Wed 5/76:30 amSTL - ONT

1 stop11h 02mAlaska Airlines

Wed 5/1411:46 amONT - STL

1 stop10h 13mAlaska Airlines

Deal found 4/30

$418

Wed 5/710:36 amSTL - ONT

2 stops9h 47mAmerican Airlines

Wed 5/1412:41 pmONT - STL

1 stop8h 04mAmerican Airlines

Deal found 4/30

$424

Fri 5/96:53 pmSTL - ONT

1 stop7h 06mFrontier

Sun 5/256:00 amONT - STL

1 stop5h 40mFrontier

Deal found 4/30

$178

Fri 5/96:53 pmSTL - ONT

1 stop7h 06mMultiple Airlines

Sun 5/1112:16 pmONT - STL

3 stops29h 54mMultiple Airlines

Deal found 4/30

$319

Fri 5/95:20 amSTL - ONT

2 stops11h 05mUnited Airlines

Sat 5/241:33 pmONT - STL

1 stop8h 26mUnited Airlines

Deal found 4/30

$467

Fri 5/93:08 pmSTL - ONT

1 stop10h 51mAlaska Airlines

Tue 5/1311:46 amONT - STL

1 stop10h 13mAlaska Airlines

Deal found 4/30

$436

Fri 5/165:00 amSTL - ONT

2 stops8h 50mAmerican Airlines

Sun 5/1810:53 amONT - STL

1 stop5h 28mAmerican Airlines

Deal found 4/30

$406

Mon 5/193:40 pmSTL - ONT

1 stop8h 49mDelta

Wed 5/284:57 pmONT - STL

1 stop5h 36mDelta

Deal found 4/30

$412

Wed 5/215:20 amSTL - ONT

2 stops11h 05mUnited Airlines

Sun 5/251:33 pmONT - STL

1 stop5h 15mUnited Airlines

Deal found 4/30

$402

Fri 5/233:00 pmSTL - ONT

2 stops8h 10mSouthwest

Sun 5/257:00 amONT - STL

2 stops9h 10mSouthwest

Deal found 4/30

$465

One-way flights from St. Louis to Ontario
Search for one-way flight options from St. Louis to Ontario. Find affordable one-way fares based on user searches. Data last updated May 1, 2025.

Sat 5/108:15 pmSTL - ONT

1 stop5h 44mFrontier

Deal found 4/30

$87

Tue 6/102:23 pmSTL - ONT

2 stops10h 23mDelta

Deal found 4/29

$153

Tue 8/129:23 amSTL - ONT

2 stops9h 01mAmerican Airlines

Deal found 4/30

$159

Thu 8/213:35 pmSTL - ONT

1 stop10h 24mAlaska Airlines

Deal found 4/30

$192

Tue 6/35:27 pmSTL - ONT

1 stop6h 59mUnited Airlines

Deal found 4/30

$199

Sun 8/246:00 amSTL - ONT

1 stop10h 09mHawaiian Airlines

Deal found 4/30

$208

Sun 6/155:50 amSTL - ONT

2 stops9h 00mSouthwest

Deal found 4/30

$244

Cheapflights Fare Finder

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

Fly from

Fly to

Route

Depart

Return

Price

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Mon 5/12

9:55 pm-12:08 pm

1 stop16h 13m

Ontario

Sun 5/18

12:59 am-9:09 am

1 stop6h 10m

$188

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Wed 7/23

3:42 pm-10:27 pm

1 stop8h 45m

Ontario

Wed 7/30

10:05 pm-8:26 am

1 stop8h 21m

$307

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Wed 9/10

3:35 pm-11:59 pm

1 stop10h 24m

Ontario

Mon 9/15

11:39 am-11:59 pm

1 stop10h 20m

$324

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Sat 6/7

3:08 pm-9:38 pm

2 stops8h 30m

Ontario

Wed 6/11

12:55 pm-11:00 pm

2 stops8h 05m

$359

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Mon 5/12

6:00 am-3:32 pm

2 stops11h 32m

Ontario

Sun 5/18

12:59 am-9:09 am

1 stop6h 10m

$368

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Wed 9/10

3:35 pm-11:59 pm

1 stop10h 24m

Ontario

Mon 9/15

7:10 am-11:59 pm

2 stops14h 49m

$385

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Tue 7/22

1:42 pm-10:52 pm

2 stops11h 10m

Ontario

Tue 7/29

5:05 am-12:46 pm

1 stop5h 41m

$402

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Fri 5/23

3:00 pm-9:10 pm

2 stops8h 10m

Ontario

Sun 5/25

7:00 am-6:10 pm

2 stops9h 10m

$465

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Sat 5/10

8:15 pm-11:59 pm

1 stop5h 44m

$87

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Tue 6/10

2:23 pm-10:46 pm

2 stops10h 23m

$153

Flights are sorted by cheapest round-trip flights first.

Deals found on 4/30

Showing 1-10 of 15 results

Compare providers for flights from St. Louis to Ontario

Use the table below to compare price accuracy, trust ratings, and cancellation policies for each provider offering flight deals from St. Louis to Ontario in May.

Provider	Price Accuracy	Trust Score*
Expedia	Price Accuracy1 star	Trust Score*3 stars
FlightHub	Price Accuracy3 stars	Trust Score*2 stars
eDreams	Price Accuracy3 stars	Trust Score*3 stars
Priceline	Price Accuracy2 stars	Trust Score*3 stars
Mytrip	Price Accuracy3 stars	Trust Score*3 stars

*The Trust Score is based on feedback from users after their booking experience. It measures overall satisfaction, helping us identify issues like hidden fees, problems during the ticketing process, and the quality of customer service. This score is our best indicator of the provider's quality and reliability.

Most accurate provider: When it comes to deals on St. Louis-Ontario flights, users find the pricing of Mytrip to be most consistent on Cheapflights vs. Mytrip Users can find the same prices on St. Louis-Ontario flight deals on Cheapflights vs. Mytrip >95% of the time. Price accuracy is based on data collected from St. Louis-Ontario flight searches over the past month and is updated monthly.
Most trusted provider: When it comes to deals on St. Louis-Ontario flights, Cheapflights users trust Mytrip the most. Mytrip has received a user feedback score of 3 out of 3 stars (3 being the best), meaning they have been trusted the most by Cheapflights users looking for St. Louis-Ontario flight deals. Provider user feedback score is based on Cheapflights searches over the past month and is updated monthly.

Best time to book a flight from St. Louis to Ontario

Have a flexible travel schedule? Discover the best time to fly to Ontario from St. Louis 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 St. Louis to Ontario

How far ahead should I book a flight from St. Louis to Ontario?

The price you pay for your flight from St. Louis to Ontario may vary depending on when you book. For the best chance of a lower fare, look to book 66 days in advance of your trip. Fares are likely to increase a fortnight or so before your departure date.

What is the cheapest month to book a flight from St. Louis to Ontario?

Currently, August is the cheapest month in which you can book a flight from St. Louis to Ontario (average of $246). Flying from St. Louis to Ontario in March is currently the most expensive (average of $328). 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 STL to ONT?

It’s optimal to fly from St. Louis to Ontario in the afternoon. By choosing this option you can save up to 19% on the cost of your flight, compared to a flight in the morning.

What is the cheapest day to fly from St. Louis to Ontario?

Travelers seeking maximum savings on their St. Louis to Ontario flight should consider departing on Monday evenings 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.

Rainfall in Ontario by month

In terms of precipitation, rainfall in Ontario ranges from 0.1 - 3.4 inches per month. February is typically the wettest month, when rainfall can reach 3.4 in. June is typically the driest time to visit Ontario when rainfall is around 0.1 in.

Temperature in Ontario by month

If weather is an important factor for your trip to Ontario, use this chart to help with planning. For those seeking warmer temperatures, August is the ideal time of year to visit, when temperatures reach an average of 78.8 F. Travelers looking to avoid the cold should look outside of December, when temperatures are typically at their lowest (around 53.6 F).

Reviews of airlines servicing Ontario

Peruse reviews from past customers who have flown with Alaska Airlines, Southwest and Delta from St. Louis to Ontario to help guide your decision. In addition to providing an overall rating, users have also rated airlines in terms of entertainment options, comfort, food, crew/service, and boarding process.

Alaska Airlines

8.0

Very good

9,972 reviews

Reviews

1 / 20

10.0

Excellent

James,Apr 2025

LAX - SFO

Good flight except the uncontrollable cold air from the ceiling.

Alaska Airlines

8.0

Very good

9,972 reviews

Alaska Airlines

8.0

Very good

9,972 reviews

Reviews

1 / 20

10.0

Excellent

James,Apr 2025

LAX - SFO

Good flight except the uncontrollable cold air from the ceiling.

Southwest

8.0

Very good

4,294 reviews

Alaska Airlines

8.0

Very good

9,972 reviews

Reviews

1 / 20

10.0

Excellent

James,Apr 2025

LAX - SFO

Good flight except the uncontrollable cold air from the ceiling.

Delta

8.0

Very good

7,934 reviews

Alaska Airlines

8.0

Very good

9,972 reviews

Reviews

1 / 20

10.0

Excellent

James,Apr 2025

LAX - SFO

Good flight except the uncontrollable cold air from the ceiling.

Hawaiian Airlines

7.9

Good

2,409 reviews

Alaska Airlines

8.0

Very good

9,972 reviews

Reviews

1 / 20

10.0

Excellent

James,Apr 2025

LAX - SFO

Good flight except the uncontrollable cold air from the ceiling.

United Airlines

7.4

Good

8,696 reviews

Alaska Airlines

8.0

Very good

9,972 reviews

Reviews

1 / 20

10.0

Excellent

James,Apr 2025

LAX - SFO

Good flight except the uncontrollable cold air from the ceiling.

Related info for your journey

What are the cheapest airlines flying from St. Louis to Ontario round-trip?
Frontier, at $188, was found to be the cheapest airline from St. Louis to Ontario.Alternate airlines to your destination round-trip include Delta and Hawaiian Airlines. Frontier is priced at 47% lower than the current average price of a flight leaving 3 months from now.
What are the cheapest airlines to fly from St. Louis to Ontario one-way?
The cheapest airline one-way is Frontier, with whom users have recently found tickets for as low as $87. However, be on the lookout for offers from Delta and American Airlines, as they are both options that can get you from St. Louis to Ontario for a low price.
Can I find deals for flights from St. Louis to Ontario that include hotel bookings?
Yes. In addition to deals on St. Louis to Ontario flights, Cheapflights offers vacation packages that include both flights and hotel.
How can I find direct flights from St. Louis to Ontario?
After entering your origin and destination, apply the non-stop filter on the search result page to find direct flights from St. Louis to Ontario.
Can I find deals for business class flights from St. Louis to Ontario?
Yes. Cheapflights offers flight deals from St. Louis 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 St. Louis to Ontario?
Currently, August is the cheapest month in which you can book a flight from St. Louis to Ontario (average of $246). Flying from St. Louis to Ontario in March is currently the most expensive (average of $328). 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

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Other flights to Ontario

Top 5 airlines flying from St. Louis to Ontario

Airline	Cheapest	Average	Flexibility	On-time
Frontier	Cheapest$128	Average$232	FlexibilityNo cancel fee	On-time62%
Delta	Cheapest$181	Average$362	FlexibilityNo cancel fee	On-timeN/A
American Airlines	Cheapest$281	Average$409	FlexibilityNo cancel fee	On-time71%
United Airlines	Cheapest$326	Average$417	FlexibilityNo cancel fee	On-time69%
Southwest	Cheapest$341	Average$408	FlexibilityNo cancel fee	On-time63%

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$87+ Cheap flights from St. Louis to Ontario (STL - 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 5/10. Fares are subject to change and may not be available on all flights or dates of travel.

Find cheap flights from St. Louis to Ontario with Cheapflights

1. Tell us where you want to go

2. Select your favorite providers

3. Compare prices and book

Cheapflights Tip: The best prices from Lambert-St Louis to Ontario are usually found in February or June, booked 68 days in advance, depart on a Tuesday or Wednesday and return on a Monday

Cheap flight deals from St. Louis to Ontario

Most accurate provider

Most trusted provider

Round-trip from

One-way from

Popular in

Cheapest in

Average price

Find flight deals from St. Louis to Ontario

Cheapest flights from St. Louis to OntarioExplore the most affordable flight options available from St. Louis to Ontario. Find the lowest fares from popular airlines and budget airlines, with prices last updated on May 1, 2025.

Explore the most affordable flight options available from St. Louis to Ontario. Find the lowest fares from popular airlines and budget airlines, with prices last updated on May 1, 2025.

Cheapflights Fare Finder

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

Compare providers for flights from St. Louis to Ontario

Provider information is updated monthly. Please note that these providers often have deals for this flight, but the availability may vary on a day-by-day basis on Cheapflights.

Use the table below to compare price accuracy, trust ratings, and cancellation policies for each provider offering flight deals from St. Louis to Ontario in May.

Best time to book a flight from St. Louis to Ontario

Have a flexible travel schedule? Discover the best time to fly to Ontario from St. Louis with our price prediction graph.

Cheapflights Insights

Everything you need to know about your flight from St. Louis to Ontario

How far ahead should I book a flight from St. Louis to Ontario?

Use this chart to determine the optimal time to book a round-trip flight from St. Louis to Ontario. Price data was last updated on April 25, 2025.

What is the cheapest month to book a flight from St. Louis to Ontario?

What is the cheapest time of day to fly from STL to ONT?

Find hourly flight availability from St. Louis 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 May 1, 2025.

What is the cheapest day to fly from St. Louis to Ontario?

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

Rainfall in Ontario by month

Plan your trip to Ontario by taking into account the average rainfall totals by month.

Temperature in Ontario by month

Plan your trip to Ontario by taking into account the average temperature totals by month.

Reviews of airlines servicing Ontario

Get insights into the airlines that provide service to Ontario. 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 Ontario. Reviews last updated May 1, 2025.

Related info for your journey

Find useful and relevant information for your journey from St. Louis to Ontario. Access travel guides, tips, and recommendations to enhance your travel experience. Get information about local attractions, weather, transportation options, and more.

What are the cheapest airlines flying from St. Louis to Ontario round-trip?

What are the cheapest airlines to fly from St. Louis to Ontario one-way?

Can I find deals for flights from St. Louis to Ontario that include hotel bookings?

How can I find direct flights from St. Louis to Ontario?

Can I find deals for business class flights from St. Louis to Ontario?

What is the cheapest month to book a flight from St. Louis to Ontario?

Browse thousands of different options on Cheapflights for your next trip

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Alternative routes for St. Louis to Ontario

See prices for flight routes from nearby airports that may be better suited for you.

Top 5 airlines flying from St. Louis to Ontario

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Cheapest flights from St. Louis to Ontario
Explore the most affordable flight options available from St. Louis to Ontario. Find the lowest fares from popular airlines and budget airlines, with prices last updated on May 1, 2025.