Cheap flights from Pennsylvania to St. Louis from $42

In general, October is the cheapest month to fly from Pennsylvania to St. Louis. Due to it being the ‘off-season’ during this time, you can expect flight prices to be around $356. The month of September is another great option to travel to St. Louis, with average flight prices from Pennsylvania averaging around $364.

The cheapest day to depart on your flight to St. Louis is on a Wednesday when prices can be found for as low as $388. 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 Sunday because tickets tend to average around $501. 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 Pennsylvania in the afternoon is the least expensive time of day to depart. momondo users have found prices as low as $409 when looking at flights departing in the afternoon. In the morning is when there is more demand to fly to St. Louis, so prices are often more expensive at around $455 per ticket.

Fly from Pittsburgh to Lambert-St Louis for the best Pennsylvania - Lambert-St Louis flight prices

You are more likely to see cheaper flights to St. Louis from Pennsylvania when booking weeks ahead of your departure date. In general, you can expect to find flights to St. Louis for around $425 when searching weeks out. However, flight prices might be lower outside of this timeframe. For example, people recently found flights to St. Louis from Pennsylvania for as low as $295 on momondo.

There are 3 cabin classes available to choose from on Pennsylvania to St. Louis flights. Cabin price and availability will vary by airline so perform a search above to find the right deals for you.

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

American Airlines, Southwest and United Airlines are the top three most popular airlines that fly to St. Louis from Pennsylvania according to our data. American Airlines is the first choice among our users, with 48% 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 August 2026, there are 29 flights per day flying from Pennsylvania to St. Louis. The most common time of day flights depart is 10:00PM, with 66% of flights taking off in the evening.

As of August 2026, there are 208 flights per week flying from Pennsylvania to St. Louis. The most common day of the week flights depart is Fri, with 22% of flights taking off on this day.