Cheap flights from Illinois to Los Angeles from $100

In general, December is the cheapest month to fly from Illinois to Ontario. Due to it being the ‘off-season’ during this time, you can expect flight prices to be around $107. If you aren’t able to travel during the month of December, then book flights to Ontario from Illinois during July instead. Flights to Ontario in July, while not as cheap as those in December, still average around $118.

The cheapest day to depart on your flight to Ontario is on a Wednesday when prices can be found for as low as $434. This is often the case because there is less demand to fly during this day of the week. When flying out on a Monday, the most expensive travel day of the week, you can expect to see flight prices from Illinois to Ontario for around $648.

In the afternoon is the cheapest time of day to fly from Illinois to Ontario when you can find flight prices for as low as $418. Flying to Ontario in the afternoon is an ideal time because this is during off-peak travel hours. If you have a flexible travel schedule, then try to avoid flying in the morning when prices are $534 on average. Flights to Ontario from Illinois in the morning are generally more expensive because this time of day is more convenient for travelers’ schedules.

Fly from Chicago O'Hare Intl to Ontario for the best Illinois - Ontario flight prices

There are 4 cabin classes available to choose from on Illinois to Ontario flights. Cabin price and availability will vary by airline so perform a search above to find the right deals for you.

You could potentially save up to 9% on your flight if you consider stops on a Illinois to Ontario flight.

Delta, Southwest, and Frontier are the most popular carriers operating from Illinois to Ontario

American Airlines, United Airlines and Frontier are the top three most popular airlines that fly to Ontario from Illinois according to our data. American Airlines is the first choice among our users, with 45% of people opting to fly with this airline when traveling to Ontario. Keep in mind that there are 7 different airlines that fly to Ontario on a routine basis, so you have a few additional options to choose from.

As of June 2026, 2 flights take off from Illinois and land in Ontario each day. The most common flight departure time for this route is 11:00AM, with 55% of daily flights taking off in the evening.

14 flights are operational weekly from Illinois to Ontario as of June 2026. The most popular departure day for this route is Mon, with 21% of flights per week taking off on this day.