Cheap flights from St. Louis to Philadelphia from $45

The cheapest month to fly to Philadelphia from St. Louis is in September. Flight prices, which tend to average around $373, are often lower during this time because this is during the off-season. The month of January is another great option to travel to Philadelphia, with average flight prices from St. Louis averaging around $384.

The cheapest day to depart from St. Louis to Philadelphia is on a Friday. Travelers who choose to depart for Philadelphia on a Friday will often find tickets for as low as $523. On the other hand, Saturday is the most expensive day to depart from St. Louis because it is more convenient for both business and leisure travelers. As a result, prices tend to be around $703.

According to our data, the cheapest time of day to fly to Philadelphia is in the evening. momondo users have found flights departing from St. Louis to Philadelphia in the evening for as low as $471. Keep in mind that these prices may fluctuate based on what airline you choose and the time of year you plan to travel. In contrast, the most expensive time of day to depart to Philadelphia is at noon when prices are around $881.

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

You are more likely to see cheaper flights to Philadelphia from St. Louis when booking weeks ahead of your departure date. In general, you can expect to find flights to Philadelphia for around $438 when searching weeks out. However, flight prices might be lower outside of this timeframe. For example, people recently found flights to Philadelphia from St. Louis for as low as $364 on momondo.

There are 4 cabin classes available to choose from on St. Louis to Philadelphia 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 65% on your flight if you consider stops on a St. Louis to Philadelphia flight.

As of September 2026, prices for St. Louis to Philadelphia flights are approximately 65% more expensive when compared to flights at the same time last year.

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

American Airlines, United Airlines and Southwest are the top three most popular airlines that fly to Philadelphia from St. Louis according to our data. American Airlines is the first choice among our users, with 35% of people opting to fly with this airline when traveling to Philadelphia. Keep in mind that there are 5 different airlines that fly to Philadelphia on a routine basis, so you have a few additional options to choose from.

As of September 2026, 4 flights take off from St. Louis and land in Philadelphia each day. The most common flight departure time for this route is 11:00AM, with 69% of daily flights taking off at noon.

The number of flights available between St. Louis and Philadelphia is 28 per week as of September 2026. The most frequent departure day is Wed, with 36% of weekly flights leaving on this day.