$163 Cheap Frontier Airlines flights San Diego (SAN) to St. Louis (STL)

You'll find cheap round-trip Frontier Airlines flights from $269 from SAN to STL by filtering your results from "Price (lowest to highest)" on Expedia. Or look for options from $163 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.

Look for cheap Frontier Airlines flights from San Diego Intl. Airport (SAN) to Lambert-St. Louis Intl. Airport (STL) one to three months prior to 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 itinerary, the ideal day to book a domestic flight is generally Sunday and the most expensive is typically 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.

Sort your results by "Early Morning" and "Morning" to find the earliest departures from SAN to STL. Heading 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.

Offering a rewarding loyalty program, Frontier Airlines is a top pick for many travelers journeying from SAN to STL. Plus, as a Frontier Miles and One Key™ member booking through Expedia, you could 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.