Cheap flights from Illinois to Los Angeles from $114

In general, September 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 $334. If you aren’t able to travel during the month of September, then book flights to Ontario from Illinois during October instead. Flights to Ontario in October, while not as cheap as those in September, still average around $348.

The cheapest day to depart on your flight to Ontario is on a Thursday when prices can be found for as low as $395. 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 $718.

At noon is the cheapest time of day to fly from Illinois to Ontario when you can find flight prices for as low as $271. Flying to Ontario at noon 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 evening when prices are $495 on average. Flights to Ontario from Illinois in the evening 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

You are more likely to see cheaper flights to Ontario from Illinois when booking weeks ahead of your departure date. In general, you can expect to find flights to Ontario for around $438 when searching weeks out. However, flight prices might be lower outside of this timeframe. For example, people recently found flights to Ontario from Illinois for as low as $261 on momondo.

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.

United Airlines, Delta, and Southwest 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 44% 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.

5 flights are operational weekly from Illinois to Ontario as of October 2026. The most popular departure day for this route is Mon, with 60% of flights per week taking off on this day.

Average flight duration from Illinois to Ontario depends on which airport you fly into and out of. Flying from Chicago to Los Angeles is 4h 26m on average, while flying from Peoria to Los Angeles is 6h 30m on average. Los Angeles is the most popular airport in Ontario.