Cheap Flights from Seattle (SEA) to St. Louis (CPS)

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Flights from Seattle (SEA) to St. Louis (CPS)
Origin airport
Seattle - Tacoma Intl.
Destination airport
St. Louis Downtown
Distance
1720 mi

Seattle to St. Louis Flights

The cheapest times to fly from Seattle to St. Louis

On average, Thursday can be the cheapest time to fly, according to data from the Airlines Reporting Corporation (ARC), one of the world's biggest databases for global airline sales. The data reveals that you could save up to 16% by flying on a Thursday—the cheapest day to travel on average—instead of a Sunday—the most expensive. Some of the most affordable flights from Seattle to St. Louis are during the month of . You can find some of the cheapest flights from Seattle to St. Louis with Expedia's search tool and vast selection of airlines.

The best time to book a flight from Seattle to St. Louis

Sunday is one of the best days to book for cheap flights from Seattle to St. Louis: Tickets reserved on a Sunday cost between 6% and 13% less than those reserved on a Friday, according to ARC data. The data also suggests booking early can also lead to cheaper airfares. You could save 24% by buying your tickets for domestic flights at least a month in advance and 10% by booking international flights 2 months in advance.

How to find cheap round-trip tickets from Seattle to St. Louis

Being flexible with your dates and using Expedia's Price Drop Protection and Price Tracking features are some of the best ways of finding a cheap ticket from Seattle to St. Louis in 2025. You can also book with separate airlines for your outbound and return journeys, from one-way. Expedia also offers Price Drop Protection, so if the cost of your airfare goes down after booking, you'll receive a credit for the difference*. This is available for a small fee, and is free to One Key Gold and Platinum tier members.

Expedia's Price Tracking feature means you can stay on top of airfares without manually checking every day. It sends you automated price alerts for cheap Seattle to St. Louis flights and uses historical data to indicate when the best time to book is. Download Expedia's free app to activate this handy tool in a few easy taps.

You could also save big by booking one of Expedia's vacation packages. Bundling together your Seattle to St. Louis airfare with your accommodations and car rental is often cheaper than booking everything separately. There’s also One Key, Expedia's generous rewards program. Join for free and you could earn One Key cash on most bookings to save on future adventures.

*Terms apply.

Disclaimer: ARC The statistics are based on average round-trip ticket prices between January and August 2023. The percentages you see are averages.

Frequently asked questions

Is it cheaper to buy a plane ticket from Sea-Tac Airport to CPS last minute?
When it’s time to book your flights, it’s always better to be prepared. While you could find a last-minute deal on a Sea-Tac Airport to St. Louis Downtown Airport (CPS) flight, prices usually don’t get cheaper as the date of departure nears. Based on flight pricing and demand studies in 2022, we have found that the sweet spot to lock in a domestic flight is between 28 – 35 days ahead. For international travel it’s three to four months.
What airports do you fly into for East St. Louis from Seattle?
From Seattle, you can fly into East St. Louis via St. Louis Downtown Airport (CPS), Lambert-St. Louis Intl. Airport (STL) and MidAmerica-St. Louis Airport (BLV). It’s a good idea to check which terminal is more convenient for you before making your decision. If you opt for St. Louis Downtown Airport (CPS), it’s around 2 mi south of downtown. Use the cash you save when booking your airfare with Expedia to explore the city’s top sights, such as Busch Stadium and Gateway Arch.
Can I change the date of my flight from SEA to St. Louis Downtown Airport?
Quickly and easily make changes to your Seattle - Tacoma Intl. Airport (SEA) to St. Louis Downtown Airport ticket by logging in to the Expedia Trips portal. But before you make any adjustments, check the fare conditions in your itinerary to find out what the carrier will allow you to do and if change fees apply. Some carriers charge a change fee per person, on top of any difference in prices. However, if you booked in the last 24 hours, you may be able to cancel for free and book new flights. You can also check out our Customer Service portal to find the answers to your questions and to chat with our Virtual Agent.

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