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$61+ 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 4/5. Fares are subject to change and may not be available on all flights or dates of travel.
STL — ONT
Mar 10 — Mar 171
Mon 3/10
Mon 3/17
1 adult, Economy
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The best prices from Lambert-St Louis to Ontario are usually found in April or June, booked 43 days in advance, depart on a Tuesday or Wednesday and return on a Monday

Cheap flight deals from St. Louis to Ontario

Discover tips and strategies to find the most affordable flight options for your journey from St. Louis (STL) to Ontario (ONT). Learn about various techniques such as flexible date searches, comparing prices across and setting up price alerts. Use these methods to find the cheapest flights available for your travel needs. Data last updated March 5, 2025.

Most accurate provider

FlightHub
3 stars

Most trusted provider

FlightHub
3 stars

Round-trip from

$150
(CheapOair)

One-way from

$61
(Trip.com)

Popular in

September

Cheapest in

April

Average price

$404
Provider with most accurate pricing for Lambert-St Louis-Ontario flight deals.
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Provider most trusted by Cheapflights users for Lambert-St Louis-Ontario flights.
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From Lambert-St Louis to Ontario
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One-way flight from Lambert-St Louis to Ontario
Search Deals
Highest demand for flights based on searches. 7% potential increase in price ($24 potential increase over avg. RT price).
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Cheapest flight prices on average. 2% potential price decrease ($9 potential savings vs. average RT price).
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Average for round-trip flights in March 2025
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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 March 5, 2025.

This CheapOair deal was found by Cheapflights users on 3/5. 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 CheapOair is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 3/197:03 pmSTL - ONT
1 stop7h 01mFrontier
Tue 3/2512:59 amONT - STL
1 stop6h 17mFrontier
Deal found 3/5$150
This Delta deal was found by Cheapflights users on 3/4. 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 3/255:00 pmSTL - ONT
1 stop8h 56mDelta
Mon 3/315:15 pmONT - STL
1 stop5h 17mDelta
Deal found 3/4$331
This Southwest deal was found by Cheapflights users on 3/4. 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.
Wed 4/210:25 amSTL - ONT
2 stops8h 40mSouthwest
Thu 4/38:50 amONT - STL
1 stop7h 25mSouthwest
Deal found 3/4$336
This American Airlines deal was found by Cheapflights users on 3/5. 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.
Fri 4/186:20 pmSTL - ONT
1 stop5h 38mAmerican Airlines
Mon 4/2110:40 pmONT - STL
1 stop7h 50mAmerican Airlines
Deal found 3/5$347
This Alaska Airlines deal was found by Cheapflights users on 3/4. 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.
Tue 4/223:08 pmSTL - ONT
1 stop26h 24mAlaska Airlines
Tue 4/296:00 amONT - STL
1 stop15h 59mAlaska Airlines
Deal found 3/4$362
This United Airlines deal was found by Cheapflights users on 3/5. 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.
Wed 4/28:48 amSTL - ONT
1 stop5h 50mUnited Airlines
Wed 4/95:00 amONT - STL
1 stop5h 47mUnited Airlines
Deal found 3/5$421
This Expedia deal was found by Cheapflights users on 3/3. 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.
Sun 4/66:44 amSTL - ONT
2 stops12h 18mMultiple Airlines
Thu 4/1012:59 amONT - STL
1 stop6h 07mMultiple Airlines
Deal found 3/3$527

Find flights from St. Louis to Ontario within your budget

Customize your flight search to find flights from St. Louis 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 March 5, 2025.

Fly from

St. Louis

Fly to

Ontario

Route

Depart

Return

Price

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Wed 3/19

7:03 pm-12:04 am

1 stop7h 01m

Ontario

Tue 3/25

12:59 am-9:16 am

1 stop6h 17m

$150

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Tue 3/25

5:00 pm-11:56 pm

1 stop8h 56m

Ontario

Mon 3/31

5:15 pm-12:32 am

1 stop5h 17m

$331

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Wed 4/2

10:25 am-5:05 pm

2 stops8h 40m

Ontario

Thu 4/3

8:50 am-6:15 pm

1 stop7h 25m

$336

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Wed 3/26

6:44 am-11:59 pm

2 stops19h 15m

Ontario

Tue 4/1

11:33 am-11:59 pm

1 stop10h 26m

$343

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Fri 4/18

6:20 pm-9:58 pm

1 stop5h 38m

Ontario

Mon 4/21

10:40 pm-8:30 am

1 stop7h 50m

$347

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Wed 4/2

8:48 am-12:38 pm

1 stop5h 50m

Ontario

Wed 4/9

5:00 am-12:47 pm

1 stop5h 47m

$421

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Sun 4/6

6:44 am-5:02 pm

2 stops12h 18m

Ontario

Thu 4/10

12:59 am-9:06 am

1 stop6h 07m

$527

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Sat 4/5

6:51 pm-11:59 pm

1 stop7h 08m

$61

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Sat 4/5

3:44 pm-9:58 pm

2 stops8h 14m

$177

St. LouisOntario

STL - ONT

STLONT

Lambert-St Louis

Tue 4/15

6:44 am-11:59 pm

2 stops19h 15m

$183

Flights are sorted by cheapest round-trip flights first.

Deals found on 3/5

Showing 1-10 of 13 results
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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 March.
ProviderPrice AccuracyTrust Score*
ExpediaPrice Accuracy1 starTrust Score*3 stars
FlightHubPrice Accuracy3 starsTrust Score*3 stars
eDreamsPrice Accuracy3 starsTrust Score*3 stars
PricelinePrice Accuracy1 starTrust Score*3 stars
MytripPrice Accuracy3 starsTrust 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 FlightHub to be most consistent on Cheapflights vs. FlightHub Users can find the same prices on St. Louis-Ontario flight deals on Cheapflights vs. FlightHub >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 FlightHub the most. FlightHub 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.

Travel insights for flights from St. Louis to Ontario

Get recent, data-driven insights about flights from St. Louis to Ontario including ideal travel times, pricing trends, and more.

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 February 28, 2025.

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 43 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 $313). 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?

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 March 5, 2025.

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?

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.

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

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

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

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 March 5, 2025.
Peruse reviews from past customers who have flown with Southwest, Alaska Airlines 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.
Southwest
8.1
Very good
4,321 reviews

Entertainment

7.6

Food

7.1

Overall

8.1

Boarding

8.2

Crew

8.7

Comfort

8.1

Reviews

1 / 20

10.0
Excellent

Merlyn,Feb 2025

LAX - SMF

New Terminal is neat, lost of stores and places to catch a bite.

Southwest
8.1
Very good
4,321 reviews
Southwest
8.1
Very good
4,321 reviews

Entertainment

7.6

Food

7.1

Overall

8.1

Boarding

8.2

Crew

8.7

Comfort

8.1

Reviews

1 / 20

10.0
Excellent

Merlyn,Feb 2025

LAX - SMF

New Terminal is neat, lost of stores and places to catch a bite.

Alaska Airlines
8.0
Very good
9,711 reviews
Southwest
8.1
Very good
4,321 reviews

Entertainment

7.6

Food

7.1

Overall

8.1

Boarding

8.2

Crew

8.7

Comfort

8.1

Reviews

1 / 20

10.0
Excellent

Merlyn,Feb 2025

LAX - SMF

New Terminal is neat, lost of stores and places to catch a bite.

Delta
8.0
Very good
8,044 reviews
Southwest
8.1
Very good
4,321 reviews

Entertainment

7.6

Food

7.1

Overall

8.1

Boarding

8.2

Crew

8.7

Comfort

8.1

Reviews

1 / 20

10.0
Excellent

Merlyn,Feb 2025

LAX - SMF

New Terminal is neat, lost of stores and places to catch a bite.

United Airlines
7.4
Good
8,655 reviews
Southwest
8.1
Very good
4,321 reviews

Entertainment

7.6

Food

7.1

Overall

8.1

Boarding

8.2

Crew

8.7

Comfort

8.1

Reviews

1 / 20

10.0
Excellent

Merlyn,Feb 2025

LAX - SMF

New Terminal is neat, lost of stores and places to catch a bite.

American Airlines
7.2
Good
10,000 reviews
Southwest
8.1
Very good
4,321 reviews

Entertainment

7.6

Food

7.1

Overall

8.1

Boarding

8.2

Crew

8.7

Comfort

8.1

Reviews

1 / 20

10.0
Excellent

Merlyn,Feb 2025

LAX - SMF

New Terminal is neat, lost of stores and places to catch a bite.

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?

    Frontier, at $150, was found to be the cheapest airline from St. Louis to Ontario.Alternate airlines to your destination round-trip include Delta and Southwest. Frontier is priced at 54% 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 $61. However, be on the lookout for offers from American Airlines and Alaska 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 $313). 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 St. Louis 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 St. Louis to Ontario

Discover the top 5 airlines that operate flights from St. Louis 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 March 5, 2025.
AirlineCheapestAverageFlexibilityOn-time
FrontierCheapest$122Average$216FlexibilityNo cancel feeOn-time62%
DeltaCheapest$171Average$385FlexibilityNo cancel feeOn-timeN/A
American AirlinesCheapest$306Average$442FlexibilityNo cancel feeOn-time71%
United AirlinesCheapest$326Average$507FlexibilityNo cancel feeOn-time69%
SouthwestCheapest$341Average$419FlexibilityNo cancel feeOn-time63%
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