$99 Cheap Delta flights Denver (DEN) to Ontario (ONT)

Set the "Price (lowest to highest)" filter on Expedia to look for cheap Delta Air Lines round-trip flights from DEN to ONT. Affordable one-way tickets from $99 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.

To find cheap Delta Air Lines fares from Denver Intl. Airport (DEN) to Los Angeles - Ontario Intl. Airport (ONT), 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 impact the cost. Sunday tends to be the most affordable, while Monday is often the most expensive for domestic flights. You can save 6% on average by booking your journey 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 departures from DEN to ONT with Delta Air Lines, sort your results by "Morning" and "Early Morning." Choosing an early flight usually 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 an excellent in-flight experience and a rewarding loyalty program, Delta Air Lines is a popular option for many travelers heading from DEN to ONT. Plus, if you're a Delta SkyMiles and One Key™ member booking with Expedia, you could earn OneKeyCash™* on eligible flights on top of your airline miles, which can go toward future travel purchases.*OneKeyCash™ disclaimer - OneKeyCash™ is not redeemable for cash and can only be used on Expedia, Hotels.com and Vrbo.