Cheap flights from St. Louis to Seattle from $140

In general, February is the cheapest month to fly from St. Louis to Seattle. Due to it being the ‘off-season’ during this time, you can expect flight prices to be around $237. If you don’t want to visit Seattle in February, then you should wait until October to fly from St. Louis, when ticket prices are also cheap, with an average price of $257.

On average, the least expensive day to fly to Seattle from St. Louis is on a Tuesday. momondo users have found tickets for Tuesday departures for as low as $413. However, this price may fluctuate depending on the airline, the season, and holidays. On the other hand, Sunday 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 $493.

Flying to Seattle from St. Louis in the afternoon is the least expensive time of day to depart. momondo users have found prices as low as $404 when looking at flights departing in the afternoon. Flights to Seattle are more costly in the morning, with an average ticket price of $496. Departure times in the morning fall within the peak daily travel times, which is why tickets can be more expensive.

Fly from Lambert-St Louis to Seattle/Tacoma Intl for the best Lambert-St Louis - Seattle/Tacoma Intl flight prices

You are more likely to see cheaper flights to Seattle from St. Louis when booking weeks ahead of your departure date. In general, you can expect to find flights to Seattle for around $326 when searching weeks out. However, flight prices might be lower outside of this timeframe. For example, people recently found flights to Seattle from St. Louis for as low as $302 on momondo.

There are 4 cabin classes available to choose from on St. Louis to Seattle 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 8% on your flight if you consider stops on a St. Louis to Seattle flight.

As of May 2026, prices for St. Louis to Seattle flights are approximately 24% more expensive when compared to flights at the same time last year.

United Airlines and Alaska Airlines are the most popular carriers operating from Lambert-St Louis to Seattle/Tacoma Intl

Alaska Airlines, American Airlines and Southwest are the top three most popular airlines that fly to Seattle from St. Louis according to our data. Alaska Airlines is the first choice among our users, with 74% of people opting to fly with this airline when traveling to Seattle. Keep in mind that there are 7 different airlines that fly to Seattle on a routine basis, so you have a few additional options to choose from.

Denver (DEN) was the most common stop: 59% of momondo users choosing 1-stop flights on this route connected there.

Flights via Dallas (DFW) offer the lowest average round-trip price of $158.

Flights connecting via Denver (DEN) have the shortest average one-way travel time: 6h 55m.

Chicago (ORD) has the shortest average layover time for this route: 1h 02m.

As of May 2026, 5 flights take off from St. Louis and land in Seattle each day. The most common flight departure time for this route is 6:00AM, with 45% of daily flights taking off at noon.

The number of flights available between St. Louis and Seattle is 38 per week as of May 2026. The most frequent departure day is Mon, with 21% of weekly flights leaving on this day.