$39 Cheap Frontier Airlines flights St. Louis (STL) to Denver (DEN)

Landing cheap one-way Frontier Airlines flights from STL to DEN from $39 on Expedia couldn’t be simpler — just filter by “Price (lowest to highest).” Alternatively, check out our budget-friendly return fares from $78 for your next getaway.**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.

January is one of the most affordable months to travel to Denver with Frontier Airlines. You could also find excellent prices on one-way and return fares in November.

For cheap Frontier Airlines fares from Lambert-St. Louis Intl. Airport (STL) to Denver Intl. Airport (DEN), start searching one to three months before your intended departure. Securing 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 affect the cost. Sunday is typically the most affordable, while Monday is often the most expensive for domestic flights. You can save 6% on average by booking 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.

You can easily fly from Lambert-St. Louis Intl. Airport (STL) to Denver Intl. Airport (DEN) on any of Frontier Airlines’s 4 direct weekly flights. Make use of our “Nonstop” and “Airline” filters to find the Frontier Airlines flight that’ll take you to DEN at a time that suits you.

Leave Lambert-St. Louis Intl. Airport (STL) for Denver Intl. Airport (DEN) on a nonstop Frontier Airlines flight, and you’ll be in the sky for around 2h 28m.

The earliest Frontier Airlines flight from STL to DEN takes off at 7:09PM UTC-6, arriving at 8:37PM UTC-7. If you’d like to jet off later in the day, the last Frontier Airlines flight leaves STL at 7:09PM UTC-6 and touches down at DEN at 8:37PM UTC-7. Flying early is generally a smart choice as morning and mid-morning flights tend to experience fewer cancellations.**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.

Board a Frontier Airlines flight from Lambert-St. Louis Intl. Airport (STL) to Denver, and you’ll most likely come in to Denver Intl. Airport (DEN). This is the airline’s primary hub in this city.

A rewarding loyalty program and the ability to rack up points through Frontier Miles are the start of the reasons to depart from STL to DEN with Frontier Airlines. Plus, when you join Expedia’s free One Key™ program, you can earn OneKeyCash™* alongside Frontier Airlines’s loyalty program earnings. You can put it toward your future trips.*OneKeyCash™ disclaimer - OneKeyCash™ is not redeemable for cash and can only be used on Expedia, Hotels.com and Vrbo.

Frontier Airlines typically operates Airbus A321neo planes for journeys from Lambert-St. Louis Intl. Airport (STL) to Denver Intl. Airport (DEN). Remember that aircraft type can change depending on operational requirements, so the plane you’ll be on might be different on your travel date.

Changes are often free within 24 hours of making a booking, but your airline may charge a fee after that. For more details about altering your flights, go to your “Trips,” select your flight and click on “Manage Booking.” If you’d like the freedom to change your plans without extra charges, tick the “No cancel fee” or “Changes included” filter when planning your next adventure.