$75 Cheap Frontier Airlines flights Portland (PDX) to St. Louis (STL)

Scoring cheap one-way Frontier Airlines flights from PDX to STL from $75 on Expedia couldn't be simpler — just filter by "Price (lowest to highest)." Alternatively, check out our budget-friendly round-trip fares from $142 for your next adventure.**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.

Start searching one to three months ahead of your departure date to find cheaper fares on Frontier Airlines flights from Portland Intl. Airport (PDX) 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 cut 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 right, and you can enjoy significant savings on domestic trips.*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.

To find the earliest departure from PDX to STL with Frontier Airlines, filter your results by "Early Morning" and "Morning." Choosing an early flight usually means you'll 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.

With a rewarding loyalty program, Frontier Airlines is a favorite of many travelers departing from PDX to STL. Plus, if you're a Frontier Miles and One Key™ member booking through Expedia, you can 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.