$160 Cheap United flights St. Louis (STL) to San Diego (SAN)

Make use of the "Price (lowest to highest)" filter on Expedia to find cheap United Airlines return flights from $308 from STL to SAN. Affordable one-way options from $160 are also on offer.**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.

Search for affordable United Airlines flights from Lambert-St. Louis Intl. Airport (STL) to San Diego Intl. Airport (SAN) one to three months prior to your departure date. 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. No matter the fare type 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 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 the earliest departure from STL to SAN with United Airlines, sort your results by "Morning" and "Early Morning." Choosing an early flight generally means you're less likely to experience 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.

Journey from STL to SAN with United Airlines and look forward to a host of benefits starting with a rewarding loyalty program. When booking through Expedia as a United Mileage Plus 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.