Cheap flights from Chicago to St. Louis from $107

In general, October is the cheapest month to fly from Chicago to St. Louis. Due to it being the ‘off-season’ during this time, you can expect flight prices to be around $75. The month of September is another great option to travel to St. Louis, with average flight prices from Chicago averaging around $77.

The cheapest day to depart on your flight to St. Louis is on a Saturday when prices can be found for as low as $337. This is often the case because there is less demand to fly during this day of the week. If your travel schedule is flexible, try to avoid departing on a Monday because tickets tend to average around $524. These prices are subject to change though, so be sure to set up a Price Alert for flights to St. Louis.

Flying to St. Louis from Chicago at noon is the least expensive time of day to depart. momondo users have found prices as low as $338 when looking at flights departing at noon. In the evening is when there is more demand to fly to St. Louis, so prices are often more expensive at around $510 per ticket.

Fly from Chicago Midway to Lambert-St Louis for the best Chicago - Lambert-St Louis flight prices

You are more likely to see cheaper flights to St. Louis from Chicago when booking weeks ahead of your departure date. In general, you can expect to find flights to St. Louis for around $409 when searching weeks out. However, flight prices might be lower outside of this timeframe. For example, people recently found flights to St. Louis from Chicago for as low as $171 on momondo.

There are 4 cabin classes available to choose from on Chicago to St. Louis 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 Chicago to St. Louis flight.

As of July 2026, prices for Chicago to St. Louis flights are approximately 17% more expensive when compared to flights at the same time last year.

Frontier, Southwest, and Delta are the most popular carriers operating from Chicago to Lambert-St Louis

United Airlines, American Airlines and Southwest are the top three most popular airlines that fly to St. Louis from Chicago according to our data. United Airlines is the first choice among our users, with 66% of people opting to fly with this airline when traveling to St. Louis. Keep in mind that there are 5 different airlines that fly to St. Louis on a routine basis, so you have a few additional options to choose from.

Historically, on average around 20% of flights between Chicago and St. Louis have experienced a delay on any given week. The average delay length over the past 12 months has been 120 minutes.

Generally, flights departing in the morning tend to experience fewer delays. Flights in the evening have, in the past, seen delays more frequently in comparison.

Tuesday is statistically the day of the week which experiences the fewest number of delays on this flight route. Sunday has historically seen more delays on average compared to the rest of the week.

According to our data, Southwest have had the least number of delays on this route over the last 12 months; with about 13% of their flights experiencing any sort of delay.

The number of flights available between Chicago and St. Louis is 62 per day as of July 2026. The most frequent departure time is 11:00PM, with 41% of daily flights leaving in the afternoon.

As of July 2026, there are 438 flights per week flying from Chicago to St. Louis. The most common day of the week flights depart is Fri, with 18% of flights taking off on this day.