$172 Cheap Flights from Seattle (SEA) to Sidney (SDY)

View $172 flight on Wed, Dec 31, 2025Opens in a new window

Popular airlines from Seattle-Tacoma International Airport (SEA) to Sidney, MT (SDY-Sidney-Richland Municipal)

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Cheap Flights from Seattle to Sidney (SEA-SDY)

Prices were available within the past 7 days and start at $172 for one-way flights and $304 for round trip, for the period specified. Prices and availability are subject to change. Additional terms apply.

Delta
Wed, Dec 3 - Tue, Dec 16
SEA
Seattle
SDY
Sidney
$304 Roundtrip, found 7 hours ago
$304
Roundtrip
found 7 hours ago
Select Delta flight, departing Wed, Dec 3 from Seattle to Sidney, returning Tue, Dec 16, priced at $304 found 7 hours ago
Alaska Airlines
Tue, Dec 30 - Sat, Jan 17
SEA
Seattle
SDY
Sidney
$314 Roundtrip, found 7 hours ago
$314
Roundtrip
found 7 hours ago
Select Alaska Airlines flight, departing Tue, Dec 30 from Seattle to Sidney, returning Sat, Jan 17, priced at $314 found 7 hours ago
Delta
Sat, Nov 15 - Mon, Dec 1
SEA
Seattle
SDY
Sidney
$345 Roundtrip, found 6 days ago
$345
Roundtrip
found 6 days ago
Select Delta flight, departing Sat, Nov 15 from Seattle to Sidney, returning Mon, Dec 1, priced at $345 found 6 days ago
Alaska Airlines
Fri, Dec 26 - Wed, Jan 7
SEA
Seattle
SDY
Sidney
$350 Roundtrip, found 7 hours ago
$350
Roundtrip
found 7 hours ago
Select Alaska Airlines flight, departing Fri, Dec 26 from Seattle to Sidney, returning Wed, Jan 7, priced at $350 found 7 hours ago
United
Mon, Nov 24 - Mon, Dec 8
SEA
Seattle
SDY
Sidney
$356 Roundtrip, found 7 hours ago
$356
Roundtrip
found 7 hours ago
Select United flight, departing Mon, Nov 24 from Seattle to Sidney, returning Mon, Dec 8, priced at $356 found 7 hours ago
United
Thu, Jan 1 - Thu, Jan 15
SEA
Seattle
SDY
Sidney
$359 Roundtrip, found 7 hours ago
$359
Roundtrip
found 7 hours ago
Select United flight, departing Thu, Jan 1 from Seattle to Sidney, returning Thu, Jan 15, priced at $359 found 7 hours ago
Alaska Airlines
Mon, Dec 29 - Sat, Jan 17
SEA
Seattle
SDY
Sidney
$359 Roundtrip, found 7 hours ago
$359
Roundtrip
found 7 hours ago
Select Alaska Airlines flight, departing Mon, Dec 29 from Seattle to Sidney, returning Sat, Jan 17, priced at $359 found 7 hours ago
Delta
Mon, Nov 24 - Fri, Dec 12
SEA
Seattle
SDY
Sidney
$365 Roundtrip, found 7 hours ago
$365
Roundtrip
found 7 hours ago
Select Delta flight, departing Mon, Nov 24 from Seattle to Sidney, returning Fri, Dec 12, priced at $365 found 7 hours ago
Delta
Thu, Dec 4 - Wed, Dec 10
SEA
Seattle
SDY
Sidney
$375 Roundtrip, found 5 days ago
$375
Roundtrip
found 5 days ago
Select Delta flight, departing Thu, Dec 4 from Seattle to Sidney, returning Wed, Dec 10, priced at $375 found 5 days ago
Hawaiian Airlines
Mon, Nov 10 - Sat, Nov 15
SEA
Seattle
SDY
Sidney
$380 Roundtrip, found 6 days ago
$380
Roundtrip
found 6 days ago
Select Hawaiian Airlines flight, departing Mon, Nov 10 from Seattle to Sidney, returning Sat, Nov 15, priced at $380 found 6 days ago

Alternative airports near Sidney

Prices were available within the past 7 days. Prices and availability are subject to change.

Select flight to Sidney-Richland Municipal SDY. Cheapest and Closest option available. Average driving time to city center is 3 minutes. Flights from $304
SDY
Sidney-Richland Municipal
CheapestClosest
Average driving time to city center3 min
Flights from $304

Frequently asked questions

How much does a flight from Seattle - Tacoma Intl. Airport (SEA) to Sidney-Richland Municipal Airport (SDY) cost?
Get a cheap one-way flight from $172 or cheap return flight from $304 from Seattle - Tacoma Intl. Airport (SEA) to Sidney-Richland Municipal Airport (SDY) with Expedia. Enter your travel dates and sort by "Price (lowest to highest)" to see our cheapest flight offers on this route.
What is the cheapest month to fly from Seattle - Tacoma Intl. Airport (SEA) to Sidney-Richland Municipal Airport (SDY)?
December is the cheapest month to fly from SEA to SDY. Planning your trip for the off-season is often the key to landing a great deal.
What is the cheapest airline that flies from Seattle - Tacoma Intl. Airport (SEA) to Sidney-Richland Municipal Airport (SDY)?
To find the cheapest airline flying from SEA to SDY, use Expedia's filter tool. Tailor your search based on your travel style, such as preferred carriers and ideal departure window. You can then sort your results by "Price (lowest to highest)" to discover the cheapest flight right away.
How many flights per day from Seattle - Tacoma Intl. Airport (SEA) to Sidney-Richland Municipal Airport (SDY)?
You'll need to hop on a flight with a layover when traveling from Seattle - Tacoma Intl. Airport (SEA) to Sidney-Richland Municipal Airport (SDY). Direct flights don't operate daily on this route. However, simply filter your search to include one or two stops to discover an option that works for you.
What day of the week has the most flights from SEA to SDY?
You'll typically find Tuesday the quietest day for flights, while Fridays are often the busiest.* However this can vary from season to season and during public holidays or peak travel times.*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 Sidney-Richland Municipal Airport (SDY)?
Select a flight from Seattle - Tacoma Intl. Airport (SEA) to Sidney-Richland Municipal Airport (SDY) that leaves before 3 PM to reduce the risk of cancellations. Departures later than this are on average 22% more likely to be canceled.**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 Sidney-Richland Municipal Airport (SDY) last-minute?
Booking your ticket from SEA to SDY shortly before your getaway is generally more expensive. But if there's some wiggle room with your itinerary, you could score a cheap last-minute fare.
Is it cheaper to book a SEA to SDY flight and hotel package?
Securing a SEA to SDY flight and hotel package is usually cheaper than booking separately. With Expedia, you can enjoy the convenience of organizing your trip all in one place. Pick from our extensive range of stays and then add flights, activities and car rentals to your booking. Bundle it all together, and you could save hundreds of dollars.
Can I cancel or change the date of my flight from Seattle - Tacoma Intl. Airport (SEA) to Sidney-Richland Municipal Airport (SDY)?
If you booked your SEA to SDY flight in the last 24 hours, you may be able to cancel or modify it at no cost. Depending on the airline and the type of fare you have, additional charges may apply for changes beyond that time. Airline policies and contact information can be found in your itinerary or confirmation email. Or, visit our Customer Service portal if you'd like more information.

Travel information

Origin airport
Seattle - Tacoma Intl.
Destination airport
Sidney-Richland Municipal
Roundtrip price
$303
Distance
842 mi

Book with confidence

Seattle to Sidney Flights

The cheapest times to fly from Seattle to Sidney

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

 

The best time to book a flight from Seattle to Sidney

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

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 Sidney in 2025. You can also book with separate airlines for your outbound and return journeys, from $172 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 Sidney 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 Sidney 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 Sidney Flights

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*Available to One Key members.