Cheap flights from Philadelphia to St. Louis from $70

In general, September is the cheapest month to fly from Philadelphia to St. Louis. Due to it being the ‘off-season’ during this time, you can expect flight prices to be around $314. The month of August is another great option to travel to St. Louis, with average flight prices from Philadelphia averaging around $320.

The cheapest day to depart on your flight to St. Louis is on a Wednesday when prices can be found for as low as $386. 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 $467. 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 Philadelphia in the afternoon is the least expensive time of day to depart. momondo users have found prices as low as $369 when looking at flights departing in the afternoon. At noon is when there is more demand to fly to St. Louis, so prices are often more expensive at around $421 per ticket.

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

You are more likely to see cheaper flights to St. Louis from Philadelphia when booking weeks ahead of your departure date. In general, you can expect to find flights to St. Louis for around $402 when searching weeks out. However, flight prices might be lower outside of this timeframe. For example, people recently found flights to St. Louis from Philadelphia for as low as $305 on momondo.

There are 2 cabin classes available to choose from on Philadelphia to Lambert-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 40% on your flight if you consider stops on a Philadelphia to St. Louis flight.

As of March 2026, prices for Philadelphia to St. Louis flights are approximately 15% more expensive when compared to flights at the same time last year.

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

American Airlines, United Airlines and Delta are the top three most popular airlines that fly to St. Louis from Philadelphia according to our data. American Airlines is the first choice among our users, with 32% of people opting to fly with this airline when traveling to St. Louis. Keep in mind that there are 6 different airlines that fly to St. Louis on a routine basis, so you have a few additional options to choose from.

Detroit (DTW) was the most common stop: 50% of momondo users choosing 1-stop flights on this route connected there.

Flights via Detroit (DTW) offer the lowest average round-trip price of $209.

Flights connecting via Orlando (MCO) have the shortest average one-way travel time: 6h 18m.

Orlando (MCO) has the shortest average layover time for this route: 0h 51m.

As of March 2026, 4 flights take off from Philadelphia and land in St. Louis each day. The most common flight departure time for this route is 9:00PM, with 54% of daily flights taking off at noon.

34 flights are operational weekly from Philadelphia to St. Louis as of March 2026. The most popular departure day for this route is Fri, with 21% of flights per week taking off on this day.