$94 Cheap Frontier Airlines flights St. Louis (STL) to Philadelphia (PHL)

You’ll find cheap round-trip Frontier Airlines flights from $188 from STL to PHL by organizing your results from “Price (lowest to highest)” on Expedia. Or search for options from $94 for a one-way journey.**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 get away to Philadelphia with Frontier Airlines. You could also find fantastic deals on one-way and round-trip tickets in February.

Look for affordable Frontier Airlines flights from Lambert-St. Louis Intl. Airport (STL) to Philadelphia Intl. Airport (PHL) one to three months before 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 type and itinerary, the best day of the week 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.

To find out if there’s a direct route from STL to PHL with Frontier Airlines or other airlines, check the “Nonstop” filter when browsing for tickets.

To find the earliest departure from STL to PHL with Frontier Airlines, filter your results by “Morning” and “Early Morning.” Booking 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.

Get on a Frontier Airlines flight from Lambert-St. Louis Intl. Airport (STL) to Philadelphia, and you’ll probably arrive at Philadelphia Intl. Airport (PHL). This is the airline’s main hub in this destination.

Depart from STL to PHL with Frontier Airlines and you’ll enjoy a host of benefits starting with a rewarding loyalty program. When you book through Expedia as a Frontier Miles and One Key™ member, you can also earn OneKeyCash™* to use on select future travel purchases.*OneKeyCash™ disclaimer - OneKeyCash™ is not redeemable for cash and can only be used on Expedia, Hotels.com and Vrbo.

It’s usually possible to cancel or modify your flight, although there may be a charge if you booked more than 24 hours ago. Need flexible options? Make use of our “No cancel fee” or “Changes included” filter to find flights that won’t charge you extra if you have to revise your plans. To modify your booking, go to “Trips,” select your flight and click on “Manage Booking” for more information.