$143 Cheap Frontier Airlines flights Ontario (ONT) to St. Louis (STL)

View $143 flight on Sat, Jun 28, 2025Opens in a new window

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$143 Cheap Frontier Airlines flights Ontario (ONT) to St. Louis (STL)

Prices were available within the past 7 days and start at $143 for one-way flights and $286 for round trip, for the period specified. Prices and availability are subject to change. Additional terms apply.

Frontier Airlines
Fri, Jul 4 - Wed, Jul 9
ONT
Ontario
STL
St. Louis
$286 Roundtrip, found 3 hours ago
$286
Roundtrip
found 3 hours ago
Select Frontier Airlines flight, departing Fri, Jul 4 from Ontario to St. Louis, returning Wed, Jul 9, priced at $286 found 3 hours ago
Frontier Airlines
Thu, Jul 10 - Wed, Jul 16
ONT
Ontario
STL
St. Louis
$296 Roundtrip, found 4 days ago
$296
Roundtrip
found 4 days ago
Select Frontier Airlines flight, departing Thu, Jul 10 from Ontario to St. Louis, returning Wed, Jul 16, priced at $296 found 4 days ago
Frontier Airlines
Sat, Jul 5 - Thu, Jul 17
ONT
Ontario
STL
St. Louis
$300 Roundtrip, found 6 days ago
$300
Roundtrip
found 6 days ago
Select Frontier Airlines flight, departing Sat, Jul 5 from Ontario to St. Louis, returning Thu, Jul 17, priced at $300 found 6 days ago
Frontier Airlines
Thu, Jul 17 - Sat, Jul 26
ONT
Ontario
STL
St. Louis
$301 Roundtrip, found 1 hour ago
$301
Roundtrip
found 1 hour ago
Select Frontier Airlines flight, departing Thu, Jul 17 from Ontario to St. Louis, returning Sat, Jul 26, priced at $301 found 1 hour ago
Frontier Airlines
Fri, Aug 29 - Sun, Aug 31
ONT
Ontario
STL
St. Louis
$302 Roundtrip, found 2 days ago
$302
Roundtrip
found 2 days ago
Select Frontier Airlines flight, departing Fri, Aug 29 from Ontario to St. Louis, returning Sun, Aug 31, priced at $302 found 2 days ago
Frontier Airlines
Fri, Jun 27 - Mon, Jun 30
ONT
Ontario
STL
St. Louis
$305 Roundtrip, found 4 hours ago
$305
Roundtrip
found 4 hours ago
Select Frontier Airlines flight, departing Fri, Jun 27 from Ontario to St. Louis, returning Mon, Jun 30, priced at $305 found 4 hours ago
Flights from Ontario (ONT) to St. Louis (STL)
Origin airport
Los Angeles - Ontario Intl.
Destination airport
Lambert-St. Louis Intl.
Airlines serving
Alaska Airlines, American Airlines, Delta, Frontier Airlines, Hawaiian Airlines, Southwest Airlines, United
Popular airline
Delta
Distance
1541 mi
Average flight time
7 hours 15 mins

Frequently asked questions

How much is a Frontier Airlines flight from Los Angeles - Ontario Intl. Airport (ONT) to Lambert-St. Louis Intl. Airport (STL)?
You can discover budget-friendly return Frontier Airlines flights from $286 from ONT to STL by filtering your results from "Price (lowest to highest)" on Expedia. Or look for options from $143 for a one-way journey.**These prices were available on Expedia within the past 7 days, for flights departing within the next year. Prices and availability are subject to change. Additional terms apply.
What is the cheapest month to fly from ONT to STL with Frontier Airlines?
Frontier Airlines flights to St. Louis are often cheaper in the quieter months of January and February. Whether you're searching for a return or one-way ticket, you could find a better deal then.
What is the cheapest time to book flights from Los Angeles - Ontario Intl. Airport (ONT) to Lambert-St. Louis Intl. Airport (STL) with Frontier Airlines?
To find cheap Frontier Airlines fares from Los Angeles - Ontario Intl. Airport (ONT) to Lambert-St. Louis Intl. Airport (STL), start searching one to three months before your intended departure. Reserving domestic flights 34 to 86 days in advance could save you 25% compared to booking just 6 to 12 days ahead. The day you book can also influence the cost. Sunday is typically the cheapest, while Monday is often the most expensive for domestic flights. You can save 6% on average by booking your trip on a Sunday.**Ideal booking window recommendation is based on average round-trip ticket prices for January through November for 2024. Best day of the week to book recommendation is based on average round-trip ticket prices for January through October 2024. All data sourced from ARC's global airline sales database.
Does Frontier Airlines fly nonstop from Los Angeles - Ontario Intl. Airport (ONT) to Lambert-St. Louis Intl. Airport (STL)?
To figure out if there's a direct journey from ONT to STL with Frontier Airlines or another airline, check the "Nonstop" box when looking for tickets.
What is the earliest Frontier Airlines flight from ONT to STL?
Search Frontier Airlines's earliest flights from ONT to STL by checking our "Early Morning" and "Morning" filters. Not only will you arrive sooner, early departures are also 20% less likely to be canceled.**Most reliable time of the day recommendation is based on January through August 2024 flight status data sourced from OAG's global flight data platform.
What airports does Frontier Airlines fly into in St. Louis?
Catch a Frontier Airlines flight from Los Angeles - Ontario Intl. Airport (ONT) to St. Louis, and you'll most likely arrive at Lambert-St. Louis Intl. Airport (STL). This is the airline's primary hub in this city.
Why fly with Frontier Airlines from ONT to STL?
Offering a rewarding loyalty program, Frontier Airlines is a top choice for many travelers departing from ONT to STL. Plus, as a Frontier Miles and One Key™ member booking through Expedia, you could earn OneKeyCash™* on eligible flights on top of your airline miles.*OneKeyCash™ disclaimer - OneKeyCash™ is not redeemable for cash and can only be used on Expedia, Hotels.com and Vrbo.
Can I change or cancel my Frontier Airlines flight from Los Angeles - Ontario Intl. Airport (ONT) to Lambert-St. Louis Intl. Airport (STL)?
You can usually modify or cancel your flight, although there may be a charge if your booking was made more than 24 hours ago. Prefer to keep your options open? Use Expedia's "Changes included" or "No cancel fee" filter to find flights that won't charge you extra if you need to adjust your plans. To update your booking, head to "Trips," select your flight and click on "Manage Booking" for more information.

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