$138 Cheap United flights Great Falls (GTF) to San Diego (SAN)

You can find cheap return United Airlines flights from $356 from GTF to SAN by filtering your results from "Price (lowest to highest)" on Expedia. Or search for options from $138 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.

Search for cheap United Airlines flights from Great Falls Intl. Airport (GTF) to San Diego Intl. Airport (SAN) one to three months before 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. Regardless of fare type and journey, the best day to book a domestic flight is usually Sunday and the most expensive day 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 "Morning" and "Early Morning" to find the earliest flights from GTF to SAN. Setting off early means you're 20% 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.

With a rewarding loyalty program, United Airlines is a top pick for many travelers heading from GTF to SAN. Plus, as a United Mileage Plus and One Key™ member booking through Expedia, you could earn OneKeyCash™* on eligible flights along with your airline miles.*OneKeyCash™ disclaimer - OneKeyCash™ is not redeemable for cash and can only be used on Expedia, Hotels.com and Vrbo.