$94 Cheap Frontier Airlines flights St. Louis (STL) to Phoenix (PHX)

Landing cheap one-way Frontier Airlines flights from STL to PHX from $94 on Expedia is a cinch — just filter by “Price (lowest to highest).” Or check out our budget-friendly return fares from $188 for your next exciting 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.

Look for return or one-way flights to Phoenix in July or August. You could find lower fares with Frontier Airlines during these off-season months.

Look for cheap Frontier Airlines flights from Lambert-St. Louis Intl. Airport (STL) to Sky Harbor Intl. Airport (PHX) one to three months ahead of your day of 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 class and journey, the ideal day to book a domestic flight is usually Sunday and the most expensive day tends to be Monday. Passengers who book on a Sunday can save 6% on average compared to those who book their travel 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 our “Nonstop” filter when browsing for direct Frontier Airlines flights from STL to PHX. It’s also a great way to compare other airlines offering the same nonstop trip.

Search Frontier Airlines’s earliest flights from STL to PHX by checking the “Morning” and “Early Morning” filters. Not only will you arrive sooner, early departures also have a 20% less chance of being 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.

Sky Harbor Intl. Airport (PHX) is the main Phoenix hub for Frontier Airlines flights from Lambert-St. Louis Intl. Airport (STL).

Journey from STL to PHX with Frontier Airlines and enjoy a range of perks including a rewarding loyalty program. When booking through Expedia as a Frontier Miles and One Key™ member, you may also earn OneKeyCash™* to spend on select future travel purchases.*OneKeyCash™ disclaimer - OneKeyCash™ is not redeemable for cash and can only be used on Expedia, Hotels.com and Vrbo.

Changes are generally free within 24 hours of making a booking, but your airline may charge a fee after that. For further details about altering your flights, go to your “Trips,” select your flight and click on “Manage Booking.” If you’d like the freedom to make changes without additional costs, check the “Changes included” or “No cancel fee” filter when organizing your next escape.