$149 Cheap Delta flights Philadelphia (PHL) to St. Louis (STL)

Grab cheap round-trip Delta Air Lines flights from $297 from PHL to STL by sorting your results from "Price (lowest to highest)" on Expedia. Or look for bargains from $149 for a one-way trip.**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.

To find cheap Delta Air Lines fares from Philadelphia Intl. Airport (PHL) to Lambert-St. Louis Intl. Airport (STL), start searching one to three months before your planned departure. Securing domestic flights 34 to 86 days in advance could save you 25% compared to booking just 6 to 12 days ahead. The day you book can also influence the overall cost. Sunday is generally the cheapest, while Monday is often the most expensive for domestic flights. You can save 6% on average by booking your journey on a Sunday.**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.

Filter your results by "Morning" and "Early Morning" to find the earliest departures from PHL to STL. Taking off early means flight cancellations are less likely.**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.

Delta Air Lines makes flying from PHL to STL more enjoyable with an excellent in-flight experience and a rewarding loyalty program. You could even start earning points with Delta SkyMiles. Remember to join Expedia's free One Key™ rewards program to earn OneKeyCash™*, which can be redeemed on future travel.*OneKeyCash™ disclaimer - OneKeyCash™ is not redeemable for cash and can only be used on Expedia, Hotels.com and Vrbo.