$129 Cheap American Airlines flights Ontario (ONT) to St. Louis (STL)

Use the "Price (lowest to highest)" filter on Expedia to find cheap American Airlines round-trip flights from $257 from ONT to STL. Affordable one-way tickets from $129 are available as well.**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 American Airlines flights from Los Angeles - Ontario Intl. Airport (ONT) 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. No matter the fare class and journey, the best day to book a domestic flight is usually Sunday and the most expensive tends to be 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.

To find the earliest departure from ONT to STL with American Airlines, filter your results by "Morning" and "Early Morning." Choosing an early flight usually means you'll experience 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.