$113 Cheap Frontier Airlines flights St. Louis (STL) to San Francisco (SFO)

Grab cheap return Frontier Airlines flights from $215 from STL to SFO by sorting your results from "Price (lowest to highest)" on Expedia. Or look for bargains from $113 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.

To find cheap Frontier Airlines fares from Lambert-St. Louis Intl. Airport (STL) to San Francisco Intl. Airport (SFO), 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 affect what you pay. Sunday is usually the most affordable, while Monday is often the most expensive for domestic flights. You can save 6% on average by booking your flight 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.

Find Frontier Airlines's earliest flights from STL to SFO by checking the "Morning" and "Early Morning" filters. Not only will you get to your destination 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.

With a rewarding loyalty program, Frontier Airlines is a top choice for many passengers flying from STL to SFO. Plus, as a Frontier Miles and One Key™ member booking through Expedia, you can 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.