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

You can find cheap return Frontier Airlines flights from $268 from ONT to ORD by filtering your results from "Price (lowest to highest)" on Expedia. Or look for bargains from $158 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.

For cheap Frontier Airlines fares from Los Angeles - Ontario Intl. Airport (ONT) to O'Hare Intl. Airport (ORD), start searching one to three months before your intended 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 the overall price. Sunday is typically the most affordable, while Monday is often the most expensive for domestic flights. You can save 6% on average by booking 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.

Filter your results by "Early Morning" and "Morning" to browse the earliest departures from ONT to ORD. Jetting off early 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.

Offering a rewarding loyalty program, Frontier Airlines is a favorite of many passengers flying from ONT to ORD. 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.