$977 Cheap Flights from Seattle (SEA) to Sion (SIR)

View $977 flight on Sun, Mar 22, 2026Opens in a new window

Popular airlines from Seattle-Tacoma International Airport (SEA) to Sion (SIR)

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Cheap Flights from Seattle to Sion (SEA-SIR)

Prices were available within the past 7 days and start at $977 for one-way flights and $3,701 for round trip, for the period specified. Prices and availability are subject to change. Additional terms apply.

United
Sun, Mar 22 - Thu, Mar 26
SEA
Seattle
SIR
Sion
$3,701 Roundtrip, found 3 days ago
$3,701
Roundtrip
found 3 days ago
Select United flight, departing Sun, Mar 22 from Seattle to Sion, returning Thu, Mar 26, priced at $3,701 found 3 days ago
United
Sun, Mar 22 - Thu, Mar 26
SEA
Seattle
SIR
Sion
$3,870 Roundtrip, found 3 days ago
$3,870
Roundtrip
found 3 days ago
Select United flight, departing Sun, Mar 22 from Seattle to Sion, returning Thu, Mar 26, priced at $3,870 found 3 days ago
United
Sun, Mar 22 - Thu, Mar 26
SEA
Seattle
SIR
Sion
$3,970 Roundtrip, found 3 days ago
$3,970
Roundtrip
found 3 days ago
Select United flight, departing Sun, Mar 22 from Seattle to Sion, returning Thu, Mar 26, priced at $3,970 found 3 days ago
United
Sun, Mar 22 - Thu, Mar 26
SEA
Seattle
SIR
Sion
$4,590 Roundtrip, found 3 days ago
$4,590
Roundtrip
found 3 days ago
Select United flight, departing Sun, Mar 22 from Seattle to Sion, returning Thu, Mar 26, priced at $4,590 found 3 days ago

Frequently asked questions

How much does a flight from Seattle - Tacoma Intl. Airport (SEA) to Sion Airport (SIR) cost?
Secure a cheap one-way flight from $977 or cheap return flight from $3,701 from Seattle - Tacoma Intl. Airport (SEA) to Sion Airport (SIR) with Expedia. Enter your travel dates and sort by "Price (lowest to highest)" to find our cheapest flight offers on this route.
What is the cheapest month to fly from Seattle - Tacoma Intl. Airport (SEA) to Sion Airport (SIR)?
Traveling in March is a great way to save, as it's the cheapest month for flights between SEA and SIR. You'll usually find the lowest prices during the off-season.
What is the cheapest airline that flies from Seattle - Tacoma Intl. Airport (SEA) to Sion Airport (SIR)?
Use the filters on Expedia to compare different airlines and find the cheapest carrier that'll take you from SEA to SIR. Then, sort your results by "Price (lowest to highest)" to snap up a good deal.
How many flights per day from Seattle - Tacoma Intl. Airport (SEA) to Sion Airport (SIR)?
You'll need to take a flight with a layover if you're traveling from Seattle - Tacoma Intl. Airport (SEA) to Sion Airport (SIR). Direct flights don't operate daily on this route. However, just filter your search to include one or two stops to discover the best option for your trip.
What day of the week has the most flights from SEA to SIR?
Friday is generally the busiest day for flights, while Tuesday tends to be the quietest.* Remember that flight schedules can change depending on a number of factors, including the season and airline.*Busiest/quietest day to travel is based on Expedia flight demand through January to December 2024.
What is the best time to fly from Seattle - Tacoma Intl. Airport (SEA) to Sion Airport (SIR)?
To touch down at Sion Airport (SIR) on time, opt for a flight that takes off from Seattle - Tacoma Intl. Airport (SEA) before 3 PM. The likelihood of cancellations is 22% higher, on average, for departures after this hour.**Most reliable time of the day and month to travel recommendation is based on January through August 2024 flight status data sourced from OAG's global flight data platform.
Is it cheaper to buy a plane ticket from Seattle - Tacoma Intl. Airport (SEA) to Sion Airport (SIR) last-minute?
Last-minute fares from SEA to SIR are typically more expensive. For the lowest rates, start searching for flights well in advance. That being said, if your travel plans are flexible, it's possible to find a cheap fare right before your journey.
Is it cheaper to book a SEA to SIR flight and hotel package?
Compared with arranging flights and hotels separately, booking a SEA to SIR flight and hotel package with Expedia could lead to significant savings. What's more, managing everything in one place takes the hassle out of travel planning. Just secure your flights and choose from our extensive range of hotels, then personalize your trip with extras like tours, activities and car rentals.
Can I cancel or change the date of my flight from Seattle - Tacoma Intl. Airport (SEA) to Sion Airport (SIR)?
If you reserved your SEA to SIR flight within the last 24 hours, you may be able to modify or cancel it without any fees. Depending on the airline and the ticket type you purchased, additional charges may apply for changes beyond this timeframe. Airline policies and contact information can be found in your itinerary or confirmation email. Or, go to our Customer Service portal for more details.

Travel information

Origin airport
Seattle - Tacoma Intl.
Destination airport
Sion
Roundtrip price
$3,701
Distance
5285 mi

Book with confidence

Seattle to Sion Flights

The cheapest times to fly from Seattle to Sion

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 Sion are during the month of March. You can find some of the cheapest flights from Seattle to Sion with Expedia's search tool and vast selection of airlines.

 

The best time to book a flight from Seattle to Sion

Sunday is one of the best days to book for cheap flights from Seattle to Sion: 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 Sion

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 Sion in 2025. You can also book with separate airlines for your outbound and return journeys, from $977 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 Sion 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 Sion 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.

 

Seattle to Sion Flights

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*Available to One Key members.