$160 Cheap American Airlines flights St. Louis (STL) to Ontario (ONT)

Finding cheap one-way American Airlines flights from STL to ONT from $160 on Expedia couldn't be simpler --- just filter by "Price (lowest to highest)." Alternatively, check out our affordable return fares from $190 for your next getaway.**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 Lambert-St. Louis Intl. Airport (STL) to Los Angeles - Ontario Intl. Airport (ONT) one to three months ahead of your 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. Regardless of fare type and itinerary, 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.

Browse American Airlines's earliest flights from STL to ONT by selecting the "Early Morning" and "Morning" filters. Not only will you get to your destination sooner, early departures also have a 20% less chance of being canceled.**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.