Cheap United flights St. Louis (STL) to Flagstaff (FLG)

Apply the "Price (lowest to highest)" filter on Expedia to search for cheap United Airlines return flights from STL to FLG. Affordable one-way fares are available too.**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.

For cheap United Airlines fares from Lambert-St. Louis Intl. Airport (STL) to Flagstaff Pulliam Field Airport (FLG), start searching one to three months before your planned departure. Reserving 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 how much 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 trip 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.

To find the earliest departure from STL to FLG with United Airlines, filter your results by "Early Morning" and "Morning." Booking an early flight usually 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.

A rewarding loyalty program and the ability to collect points through United Mileage Plus are the start of the reasons to leave from STL to FLG with United Airlines. Plus, when you sign up to our One Key™ program, you can receive OneKeyCash™* alongside any airline loyalty program earnings. It's yours to spend on your next adventure.*OneKeyCash™ disclaimer - OneKeyCash™ is not redeemable for cash and can only be used on Expedia, Hotels.com and Vrbo.