$103 Cheap Frontier Airlines flights Phoenix (PHX) to St. Louis (STL)

Scoring cheap one-way Frontier Airlines flights from PHX to STL from $103 on Expedia couldn’t be simpler — just filter by “Price (lowest to highest).” Or check out our budget-friendly return fares from $188 for your next exciting vacation.**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.

Frontier Airlines flights to St. Louis tend to be cheaper in the quieter months of January and February. Whether you’re in search of a return or one-way ticket, you could land a better deal then.

Look for affordable Frontier Airlines flights from Sky Harbor Intl. Airport (PHX) to Lambert-St. Louis Intl. Airport (STL) one to three months prior to your departure. Travelers who book domestic flights 34 to 86 days in advance can save 25% compared to those who book just 6 to 12 days ahead. Regardless of fare type and itinerary, the best day to book a domestic flight is generally Sunday and the most expensive tends to be Monday. Passengers who book on a Sunday can save 6% on average compared to those who book on a Monday.**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.

Use the “Nonstop” filter when searching for direct Frontier Airlines flights from PHX to STL. It’s also a great way to compare other carriers offering the same direct trip.

Find Frontier Airlines’s earliest flights from PHX to STL by using the “Early Morning” and “Morning” filters. Not only will you arrive sooner, early departures also experience 20% 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.

Frontier Airlines flights from Sky Harbor Intl. Airport (PHX) to St. Louis come in to Lambert-St. Louis Intl. Airport (STL). This is the main gateway to this city.

A rewarding loyalty program and the ability to rack up points through Frontier Miles are the start of the reasons to leave from PHX to STL with Frontier Airlines. Plus, when you join our One Key™ program, you can earn OneKeyCash™* on top of any airline loyalty program earnings. It’s yours to spend on future travel plans.*OneKeyCash™ disclaimer - OneKeyCash™ is not redeemable for cash and can only be used on Expedia, Hotels.com and Vrbo.

Changes are usually free within 24 hours of making a booking, but your airline may add a charge after that. For further information about modifying your flights, check out your “Trips,” select your flight and click on “Manage Booking.” If you want the flexibility to change your itinerary without additional costs, apply the “No cancel fee” or “Changes included” filter when organizing your next break.