$104 Cheap Flights from Ontario (ONT) to St. Louis (STL)

View $104 flight on Wed, May 14, 2025Opens in a new window

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

Find available prices by choosing your travel dates.

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

Prices were available within the past 7 days and start at $104 for one-way flights and $198 for round trip, for the period specified. Prices and availability are subject to change. Additional terms apply.

Frontier Airlines
Fri, May 2 - Sat, May 3
ONT
Ontario
STL
St. Louis
$198 Roundtrip, found 7 hours ago
$198
Roundtrip
found 7 hours ago
Select Frontier Airlines flight, departing Fri, May 2 from Ontario to St. Louis, returning Sat, May 3, priced at $198 found 7 hours ago
Frontier Airlines
Mon, Apr 28 - Sat, May 3
ONT
Ontario
STL
St. Louis
$200 Roundtrip, found 2 days ago
$200
Roundtrip
found 2 days ago
Select Frontier Airlines flight, departing Mon, Apr 28 from Ontario to St. Louis, returning Sat, May 3, priced at $200 found 2 days ago
Frontier Airlines
Wed, May 7 - Fri, May 9
ONT
Ontario
STL
St. Louis
$218 Roundtrip, just found
$218
Roundtrip
just found
Select Frontier Airlines flight, departing Wed, May 7 from Ontario to St. Louis, returning Fri, May 9, priced at $218 just found
Frontier Airlines
Sat, May 10 - Sat, May 17
ONT
Ontario
STL
St. Louis
$228 Roundtrip, just found
$228
Roundtrip
just found
Select Frontier Airlines flight, departing Sat, May 10 from Ontario to St. Louis, returning Sat, May 17, priced at $228 just found
Frontier Airlines
Wed, May 14 - Mon, May 19
ONT
Ontario
STL
St. Louis
$238 Roundtrip, just found
$238
Roundtrip
just found
Select Frontier Airlines flight, departing Wed, May 14 from Ontario to St. Louis, returning Mon, May 19, priced at $238 just found
Alaska Airlines
Tue, May 13 - Sat, May 17
ONT
Ontario
STL
St. Louis
$247 Roundtrip, found 3 days ago
$247
Roundtrip
found 3 days ago
Select Alaska Airlines flight, departing Tue, May 13 from Ontario to St. Louis, returning Sat, May 17, priced at $247 found 3 days ago
Frontier Airlines
Thu, May 8 - Mon, May 12
ONT
Ontario
STL
St. Louis
$248 Roundtrip, just found
$248
Roundtrip
just found
Select Frontier Airlines flight, departing Thu, May 8 from Ontario to St. Louis, returning Mon, May 12, priced at $248 just found
United
Tue, May 20 - Thu, May 29
ONT
Ontario
STL
St. Louis
$263 Roundtrip, found 1 day ago
$263
Roundtrip
found 1 day ago
Select United flight, departing Tue, May 20 from Ontario to St. Louis, returning Thu, May 29, priced at $263 found 1 day ago
Southwest Airlines
Tue, May 20 - Thu, May 29
ONT
Ontario
STL
St. Louis
$281 Roundtrip, found 1 day ago
$281
Roundtrip
found 1 day ago
Select Southwest Airlines flight, departing Tue, May 20 from Ontario to St. Louis, returning Thu, May 29, priced at $281 found 1 day ago
American Airlines
Tue, May 20 - Tue, May 27
ONT
Ontario
STL
St. Louis
$307 Roundtrip, found 1 hour ago
$307
Roundtrip
found 1 hour ago
Select American Airlines flight, departing Tue, May 20 from Ontario to St. Louis, returning Tue, May 27, priced at $307 found 1 hour ago

Frequently asked questions

How much does a flight from Los Angeles - Ontario Intl. Airport (ONT) to Lambert-St. Louis Intl. Airport (STL) cost?
Discover the latest flight deals from ONT to STL by entering your preferred travel dates and searching on Expedia. Easily compare prices by departure date if you have flexibility with your schedule and use handy filters to explore prices for your preferred journey. As a member of One Key™, our free loyalty program, you can use Price Tracking to watch fares and receive notifications if prices go up or down.
What is the cheapest month to fly from ONT to STL?
The cheapest flights from ONT to STL are usually during off-peak season, when demand is lower. To save money, avoid flying during public holidays, school breaks and major local events.
Which airlines fly direct from Los Angeles - Ontario Intl. Airport (ONT) to Lambert-St. Louis Intl. Airport (STL)?
While Ontario, CA (ONT-Los Angeles - Ontario Intl.) has no direct flights to Lambert-St. Louis Intl. Airport (STL), other airports have nonstop routes. Taking off from Los Angeles Intl. Airport (LAX) will get you to St. Louis without any layovers.
What is the cheapest airline that flies from ONT to STL?
Use the filter tool on Expedia to compare airlines and find the cheapest carrier that’ll take you from ONT to STL. Sort your results by “Price (lowest to highest)” to snap up a great deal.
How many flights per day from Los Angeles - Ontario Intl. Airport (ONT) to Lambert-St. Louis Intl. Airport (STL)?
Direct flights from Los Angeles - Ontario Intl. Airport (ONT) to Lambert-St. Louis Intl. Airport (STL) aren’t available daily, so you’ll need to take a flight with a layover. Explore your options with Expedia’s filters. Enter your dates and click on either “1 Stop” or “2+ Stops.”
What day of the week has the most flights from ONT to STL?
Friday is generally the busiest day for flights, while Tuesday tends to be the quietest.* Just remember that flight schedules can vary based on a range of factors, such as the carrier and season.*Busiest/quietest day to travel is based on Expedia flight demand through January to December 2024.
What is the best time to fly from Los Angeles - Ontario Intl. Airport (ONT) to Lambert-St. Louis Intl. Airport (STL)?
Opt for a flight from Los Angeles - Ontario Intl. Airport (ONT) to Lambert-St. Louis Intl. Airport (STL) that takes off before 3 PM to reduce the risk of cancellations. Departures after this hour are on average 22% more likely to be canceled.**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.
Is it cheaper to buy a plane ticket from Los Angeles - Ontario Intl. Airport (ONT) to Lambert-St. Louis Intl. Airport (STL) last-minute?
Holding off until just before your departure to book a flight from ONT to STL often results in higher prices. While you may come across some last-minute discounts, there’s no guarantee. Keep your travel plans flexible for a better chance of getting a bargain.
Is it cheaper to book an ONT to STL flight and hotel package?
You’ll generally save money by securing an ONT to STL flight and hotel package compared to booking separately. In fact, travelers could save hundreds of dollars by bundling with Expedia. And it’s easy to manage it all in one convenient place. After selecting your preferred accommodations and flights, you can add extras like activities, tours and car rentals.
Can I cancel or change the date of my flight from Los Angeles - Ontario Intl. Airport (ONT) to Lambert-St. Louis Intl. Airport (STL)?
If you booked your ONT to STL flight in the last 24 hours, you may be able to modify or cancel it without fees. Depending on the airline and the type of ticket you have, additional charges may apply for changes beyond this timeframe. Airline policies and contact information can be found in your itinerary or confirmation email. Or, visit our Customer Service portal for more information.
*Available to One Key members.