Cheap flights from St. Louis to Portland from $158

The cheapest month to fly to Portland, Maine from St. Louis is in November. Flight prices, which tend to average around $326, are often lower during this time because this is during the off-season. If you aren’t able to travel to Portland, Maine during the month of November, then flying in March is also cheap. Prices for this month can be found on momondo for an average of $349.

You are more likely to see cheaper flights to Portland, Maine from St. Louis when booking weeks ahead of your departure date. In general, you can expect to find flights to Portland, Maine for around $433 when searching weeks out. However, flight prices might be lower outside of this timeframe. For example, people recently found flights to Portland, Maine from St. Louis for as low as $329 on momondo.

You could potentially save up to 24% on your flight if you consider stops on a St. Louis to Portland, Maine flight.

As of June 2026, prices for St. Louis to Portland, Maine flights are approximately 5% more expensive when compared to flights at the same time last year.

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

American Airlines, Southwest and Delta are the top three most popular airlines that fly to Portland, Maine from St. Louis according to our data. American Airlines is the first choice among our users, with 56% of people opting to fly with this airline when traveling to Portland, Maine. Keep in mind that there are 6 different airlines that fly to Portland, Maine on a routine basis, so you have a few additional options to choose from.

Philadelphia (PHL) 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 $286.

Flights connecting via Detroit (DTW) have the shortest average one-way travel time: 4h 28m.

Detroit (DTW) has the shortest average layover time for this route: 0h 54m.