$158 Cheap Frontier Airlines flights Chicago (ORD) to Ontario (ONT)

You'll find cheap return Frontier Airlines flights from $264 from ORD to ONT by filtering your results from "Price (lowest to highest)" on Expedia. Or search for options from $158 for a one-way trip.**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 Frontier Airlines flights from O'Hare Intl. Airport (ORD) to Los Angeles - Ontario Intl. Airport (ONT) one to three months prior to your departure day. 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 day 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 ORD to ONT with Frontier Airlines, filter your search by "Early Morning" and "Morning." Choosing an early flight generally means cancellations are less likely.**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, Frontier Airlines is a top pick for many passengers departing from ORD to ONT. Plus, as a Frontier Miles and One Key™ member booking through Expedia, you could earn OneKeyCash™* on eligible flights on top of your airline miles.*OneKeyCash™ disclaimer - OneKeyCash™ is not redeemable for cash and can only be used on Expedia, Hotels.com and Vrbo.