$70 Cheap Flights from St. Louis (STL) to Ontario (ONT)

View $70 flight on Sat, Nov 15, 2025Opens in a new window

Popular airlines from St. Louis Lambert Intl. Airport (STL) to Los Angeles - Ontario Intl. Airport (ONT)

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Cheap Flights from St. Louis to Ontario (STL-ONT)

Prices were available within the past 7 days and start at $70 for one-way flights and $137 for round trip, for the period specified. Prices and availability are subject to change. Additional terms apply.

Frontier Airlines
Fri, Nov 14 - Mon, Nov 17
STL
St. Louis
ONT
Ontario
$137 Roundtrip, found 5 hours ago
$137
Roundtrip
found 5 hours ago
Select Frontier Airlines flight, departing Fri, Nov 14 from St. Louis to Ontario, returning Mon, Nov 17, priced at $137 found 5 hours ago
Frontier Airlines
Thu, Dec 4 - Wed, Dec 10
STL
St. Louis
ONT
Ontario
$140 Roundtrip, found 2 hours ago
$140
Roundtrip
found 2 hours ago
Select Frontier Airlines flight, departing Thu, Dec 4 from St. Louis to Ontario, returning Wed, Dec 10, priced at $140 found 2 hours ago
Frontier Airlines
Sat, Nov 15 - Fri, Dec 5
STL
St. Louis
ONT
Ontario
$144 Roundtrip, just found
$144
Roundtrip
just found
Select Frontier Airlines flight, departing Sat, Nov 15 from St. Louis to Ontario, returning Fri, Dec 5, priced at $144 just found
Frontier Airlines
Fri, Nov 14 - Sat, Nov 15
STL
St. Louis
ONT
Ontario
$147 Roundtrip, just found
$147
Roundtrip
just found
Select Frontier Airlines flight, departing Fri, Nov 14 from St. Louis to Ontario, returning Sat, Nov 15, priced at $147 just found
Frontier Airlines
Fri, Dec 12 - Sun, Dec 14
STL
St. Louis
ONT
Ontario
$148 Roundtrip, found 2 hours ago
$148
Roundtrip
found 2 hours ago
Select Frontier Airlines flight, departing Fri, Dec 12 from St. Louis to Ontario, returning Sun, Dec 14, priced at $148 found 2 hours ago
Frontier Airlines
Fri, Nov 14 - Fri, Dec 5
STL
St. Louis
ONT
Ontario
$151 Roundtrip, just found
$151
Roundtrip
just found
Select Frontier Airlines flight, departing Fri, Nov 14 from St. Louis to Ontario, returning Fri, Dec 5, priced at $151 just found
American Airlines
Tue, Dec 9 - Tue, Dec 16
STL
St. Louis
ONT
Ontario
$287 Roundtrip, found 1 hour ago
$287
Roundtrip
found 1 hour ago
Select American Airlines flight, departing Tue, Dec 9 from St. Louis to Ontario, returning Tue, Dec 16, priced at $287 found 1 hour ago
United
Tue, Dec 9 - Tue, Dec 16
STL
St. Louis
ONT
Ontario
$287 Roundtrip, found 1 hour ago
$287
Roundtrip
found 1 hour ago
Select United flight, departing Tue, Dec 9 from St. Louis to Ontario, returning Tue, Dec 16, priced at $287 found 1 hour ago
Southwest Airlines
Tue, Dec 9 - Tue, Dec 16
STL
St. Louis
ONT
Ontario
$313 Roundtrip, found 1 hour ago
$313
Roundtrip
found 1 hour ago
Select Southwest Airlines flight, departing Tue, Dec 9 from St. Louis to Ontario, returning Tue, Dec 16, priced at $313 found 1 hour ago
Hawaiian Airlines
Fri, Jan 30 - Wed, Feb 25
STL
St. Louis
ONT
Ontario
$344 Roundtrip, found 1 day ago
$344
Roundtrip
found 1 day ago
Select Hawaiian Airlines flight, departing Fri, Jan 30 from St. Louis to Ontario, returning Wed, Feb 25, priced at $344 found 1 day ago

Find the cheapest month to fly from St. Louis (STL) to Ontario (ONT)

November is typically the cheapest month to fly

From $118 - $456 per traveler.

Alternative airports near Ontario

Prices were available within the past 7 days. Prices and availability are subject to change.

Select flight to John Wayne SNA. Average driving time to city center is 42 minutes. Flights from $340
SNA
John Wayne
Average driving time to city center42 min
Flights from $340

Frequently asked questions

How much does a flight from Lambert-St. Louis Intl. Airport (STL) to Los Angeles - Ontario Intl. Airport (ONT) cost?
Get a cheap one-way flight from $70 or cheap return flight from $137 from Lambert-St. Louis Intl. Airport (STL) to Los Angeles - Ontario Intl. Airport (ONT) with Expedia. Enter your travel dates and sort by "Price (lowest to highest)" to find our cheapest flight offers on this route.
What is the cheapest month to fly from Lambert-St. Louis Intl. Airport (STL) to Los Angeles - Ontario Intl. Airport (ONT)?
November is the most affordable month to fly from STL to ONT. Traveling during quieter months is often the key to landing a great deal.
What is the cheapest airline that flies from Lambert-St. Louis Intl. Airport (STL) to Los Angeles - Ontario Intl. Airport (ONT)?
Expedia's filter tool lets you easily compare airlines, flight times and fares all in one place. Customize the search to your preferences, then sort by "Price (lowest to highest)" to see which carrier offers the cheapest STL to ONT flight.
How many flights per day from Lambert-St. Louis Intl. Airport (STL) to Los Angeles - Ontario Intl. Airport (ONT)?
There aren't any daily nonstop flights available from Lambert-St. Louis Intl. Airport (STL) to Los Angeles - Ontario Intl. Airport (ONT). But you can opt for flights with layovers. Filter your search results on Expedia to include one or more stops, and you'll be on your way in no time.
What day of the week has the most flights from STL to ONT?
Generally you'll find the widest variety of flight choices on a Friday. Tuesdays tend to be the quietest.* But this can vary based on the season, airline and other factors.*Busiest/quietest day to travel is based on Expedia flight demand through January to December 2024.
What is the best time to fly from Lambert-St. Louis Intl. Airport (STL) to Los Angeles - Ontario Intl. Airport (ONT)?
To touch down at Los Angeles - Ontario Intl. Airport (ONT) without delays, opt for a flight that leaves Lambert-St. Louis Intl. Airport (STL) before 3 PM. The likelihood of cancellations is 22% higher, on average, for departures after this hour.**Most reliable time of the day and month to travel recommendation is based on January through August 2024 flight status data sourced from OAG's global flight data platform.
What airports do you fly into for Ontario from Lambert-St. Louis Intl. Airport (STL)?
Touch down at any one of these Ontario airports after your direct flight from Lambert-St. Louis Intl. Airport (STL):

  • Los Angeles Intl. Airport (LAX)
  • Long Beach Municipal Airport (LGB)
  • Bob Hope Airport (BUR)

Is it cheaper to buy a plane ticket from Lambert-St. Louis Intl. Airport (STL) to Los Angeles - Ontario Intl. Airport (ONT) last-minute?
Last-minute bookings from STL to ONT are generally more expensive. For the best rates, start searching for flights early. That said, if you're flexible with your travel dates, it's possible to find a cheap fare just before your departure.
Is it cheaper to book a STL to ONT flight and hotel package?
Opting for a STL to ONT flight and hotel package is typically cheaper than booking separately. With Expedia, you can enjoy the ease of organizing your trip in one place. Select from our impressive range of accommodations and then add flights, activities and car rentals to your booking. Bundle everything together, and you could save hundreds of dollars.
Can I cancel or change the date of my flight from Lambert-St. Louis Intl. Airport (STL) to Los Angeles - Ontario Intl. Airport (ONT)?
Usually, it's possible to reschedule or cancel your STL to ONT flight. However, if it's been more than 24 hours since booking, additional charges may apply. Check your airline's policies in your itinerary to see what changes are possible and whether any costs are involved. You'll also find more information on our Customer Service portal.

Travel information

Origin airport
Lambert-St. Louis Intl.
Destination airport
Los Angeles - Ontario Intl.
Airlines serving
Alaska Airlines, American Airlines, Delta, Frontier Airlines, Hawaiian Airlines, Southwest Airlines, United
Roundtrip price
$137
Distance
1541 mi

Book with confidence

St. Louis to Ontario Flights

The cheapest times to fly from St. Louis to Ontario

On average, Thursday can be the cheapest time to fly, according to data from the Airlines Reporting Corporation (ARC), one of the world's biggest databases for global airline sales. The data reveals that you could save up to 16% by flying on a Thursday—the cheapest day to travel on average—instead of a Sunday—the most expensive. Some of the most affordable flights from St. Louis to Ontario are during the month of November. You can find some of the cheapest flights from St. Louis to Ontario with Expedia's search tool and vast selection of airlines.

 

The best time to book a flight from St. Louis to Ontario

Sunday is one of the best days to book for cheap flights from St. Louis to Ontario: Tickets reserved on a Sunday cost between 6% and 13% less than those reserved on a Friday, according to ARC data. The data also suggests booking early can also lead to cheaper airfares. You could save 24% by buying your tickets for domestic flights at least a month in advance and 10% by booking international flights 2 months in advance.

 

How to find cheap round-trip tickets from St. Louis to Ontario

Being flexible with your dates and using Expedia's Price Drop Protection and Price Tracking features are some of the best ways of finding a cheap ticket from St. Louis to Ontario in 2025. You can also book with separate airlines for your outbound and return journeys, from $70 one-way. Expedia also offers Price Drop Protection, so if the cost of your airfare goes down after booking, you'll receive a credit for the difference*. This is available for a small fee, and is free to One Key Gold and Platinum tier members.

 

Expedia's Price Tracking feature means you can stay on top of airfares without manually checking every day. It sends you automated price alerts for cheap St. Louis to Ontario flights and uses historical data to indicate when the best time to book is. Download Expedia's free app to activate this handy tool in a few easy taps.

 

You could also save big by booking one of Expedia's vacation packages. Bundling together your St. Louis to Ontario airfare with your accommodations and car rental is often cheaper than booking everything separately. There’s also One Key, Expedia's generous rewards program. Join for free and you could earn One Key cash on most bookings to save on future adventures.

 

*Terms apply.

 

Disclaimer: ARC The statistics are based on average round-trip ticket prices between January and August 2023. The percentages you see are averages.

 

St. Louis to Ontario Flights

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*Available to One Key members.