Cheap flights from Illinois to St. Louis from $117

In general, December is the cheapest month to fly from Illinois to St. Louis. Due to it being the ‘off-season’ during this time, you can expect flight prices to be around $214. The month of September is another great option to travel to St. Louis, with average flight prices from Illinois averaging around $243.

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 Illinois 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 Illinois - Lambert-St Louis flight prices

You are more likely to see cheaper flights to St. Louis from Illinois when booking weeks ahead of your departure date. In general, you can expect to find flights to St. Louis for around $411 when searching weeks out. However, flight prices might be lower outside of this timeframe. For example, people recently found flights to St. Louis from Illinois for as low as $171 on momondo.

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

United Airlines, Southwest, and Frontier are the most popular carriers operating from Illinois to Lambert-St Louis

United Airlines, American Airlines and Southwest are the top three most popular airlines that fly to St. Louis from Illinois 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.

As of July 2026, there are 58 flights per day flying from Illinois to St. Louis. The most common time of day flights depart is 11:00PM, with 41% of flights taking off in the afternoon.

As of July 2026, there are 409 flights per week flying from Illinois to St. Louis. The most common day of the week flights depart is Fri, with 20% of flights taking off on this day.