$79 Cheap Frontier Airlines flights Denver (DEN) to St. Louis (STL)

Finding cheap one-way Frontier Airlines flights from DEN to STL from $79 on Expedia couldn’t be simpler — just filter by “Price (lowest to highest).” Alternatively, check out our affordable round-trip fares from $139 for your next break.**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.

Search for return or one-way flights to St. Louis in January or February. You could find lower fares with Frontier Airlines during these off-season months.

Start searching one to three months before your departure to find cheaper fares on Frontier Airlines flights from Denver Intl. Airport (DEN) to Lambert-St. Louis Intl. Airport (STL). You can save 25% by booking your domestic flight 34 to 86 days in advance versus last-minute reservations made 6 to 12 days out. You could also reduce costs by buying your fare on a Sunday, as it’s 6% cheaper on average than a Monday, the most expensive day to book.* Get your timing spot on, and you can enjoy significant savings on domestic journeys.*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.

Yes, you can travel from Denver Intl. Airport (DEN) to Lambert-St. Louis Intl. Airport (STL) on any of Frontier Airlines’s 4 weekly direct flights. Apply Expedia’s “Nonstop” and “Airline” filters to find the Frontier Airlines flight that’ll get you to STL at your preferred time.

From takeoff to touchdown, a direct Frontier Airlines flight from Denver Intl. Airport (DEN) to Lambert-St. Louis Intl. Airport (STL) typically takes 2h 16m.

Jetting off from DEN at 6:00AM UTC-7, the first Frontier Airlines flight to STL arrives at 9:16AM UTC-6. Flying early means you’ll be less likely to encounter delays or cancellations.* After something later? The last Frontier Airlines flight from DEN to STL departs at 6:00AM UTC-7 and touches down at 9:16AM UTC-6.*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.

Frontier Airlines flights from Denver Intl. Airport (DEN) to St. Louis arrive at Lambert-St. Louis Intl. Airport (STL). This is the main entry point to this destination.

A rewarding loyalty program and the opportunity to collect points through Frontier Miles are the start of the reasons to leave from DEN to STL with Frontier Airlines. Plus, when you sign up to our One Key™ program, you can receive OneKeyCash™* alongside any airline loyalty program earnings. It’s yours to use wherever your next trip takes you.*OneKeyCash™ disclaimer - OneKeyCash™ is not redeemable for cash and can only be used on Expedia, Hotels.com and Vrbo.

Set off on a Frontier Airlines flight from Denver Intl. Airport (DEN) to Lambert-St. Louis Intl. Airport (STL), and you’ll probably be on an Airbus A321neo. Keep in mind though, that the aircraft type can change due to operational needs.

Typically, you can cancel or reschedule your flight, although there may be additional fees if you booked more than 24 hours ago. Prefer to keep your options open? Use Expedia’s “No cancel fee” or “Changes included” filter to find flights that won’t penalize you if you have to adjust your plans. To modify your booking, go to “Trips,” select your flight and click on “Manage Booking” for further information.