Cheap flights from Ontario to Chicago from $99

The month of September is, on average, the cheapest month to fly to Chicago from Ontario, with most prices found around $102. If you’re not able to fly to Chicago in September, then April is your next best option. Flight prices from Ontario to Chicago during April average around $108.

The cheapest day to depart on your flight to Chicago is on a Wednesday when prices can be found for as low as $401. This is often the case because there is less demand to fly during this day of the week. When flying out on a Sunday, the most expensive travel day of the week, you can expect to see flight prices from Ontario to Chicago for around $490.

Our most recent data shows that the best time of day to fly to Chicago is in the afternoon. Flights from Ontario to Chicago during this time can be as low as $339. In contrast, the most expensive time of day to depart to Chicago is at noon when prices are around $500.

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

You are more likely to see cheaper flights to Chicago from Ontario when booking weeks ahead of your departure date. In general, you can expect to find flights to Chicago for around $416 when searching weeks out. However, flight prices might be lower outside of this timeframe. For example, people recently found flights to Chicago from Ontario for as low as $345 on momondo.

There are 4 cabin classes available to choose from on Ontario to Chicago 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 16% on your flight if you consider stops on a Ontario to Chicago flight.

As of July 2026, prices for Ontario to Chicago flights are approximately 1% more expensive when compared to flights at the same time last year.

Southwest, United Airlines, and Delta are the most popular carriers operating from Ontario to Chicago

American Airlines, United Airlines and Frontier are the top three most popular airlines that fly to Chicago from Ontario according to our data. American Airlines is the first choice among our users, with 43% of people opting to fly with this airline when traveling to Chicago. Keep in mind that there are 7 different airlines that fly to Chicago on a routine basis, so you have a few additional options to choose from.

Phoenix (PHX) was the most common stop: 38% of momondo users choosing 1-stop flights on this route connected there.

Flights via Las Vegas (LAS) offer the lowest average round-trip price of $144.

Flights connecting via Las Vegas (LAS) have the shortest average one-way travel time: 5h 40m.

Las Vegas (LAS) has the shortest average layover time for this route: 0h 45m.

As of July 2026, 2 flights take off from Ontario and land in Chicago each day. The most common flight departure time for this route is 11:00PM, with 35% of daily flights taking off in the evening.

The number of flights available between Ontario and Chicago is 17 per week as of July 2026. The most frequent departure day is Mon, with 24% of weekly flights leaving on this day.