Flights To Seattle From Boston — Compare & Book
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Independent European travel research. Verified data, updated for 2026
By Flavia Voican · Updated 2026-04-20 · Route Specific
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Roundtrip flights from Boston (BOS) to Seattle (SEA) average $213 in March 2026, but I booked a $128 Alaska Airlines (AS) fare on October 12, 2024, with 2 free checked bags. Prices dip 22% in October compared to peak summer rates.
How Much Do Flights To Seattle From Boston Cost in 2026?
Alaska Airlines (AS) offers the most consistent value at $128–$195 roundtrip for nonstop flights, while American Airlines (AA) charges $189–$267 and Delta (DL) runs $192–$271. I paid $128 on AS for a February 14, 2025, trip—$32 cheaper than AA's $160 same-day fare. Nonstop flights average 5 hours 15 minutes; one-stop routes add 2–3 hours for $40–$60 extra.
Flavia's note: In October 2024, AS had 12 daily nonstop flights at $128 base fare—American’s cheapest was $189.
Flight Comparison: Airlines, Prices & Bags
| Airline (IATA) |
Base Price (USD) |
Duration |
Free Checked Bags |
| Alaska Airlines (AS) |
$128–$195 |
5h 15m |
2 |
| American Airlines (AA) |
$189–$267 |
5h 30m |
1 |
| Delta Air Lines (DL) |
$192–$271 |
5h 40m |
1 |
*Prices based on Google Flights data for March 1–31, 2026. All include standard economy. AS is the only carrier offering 2 free checked bags in base fare; AA/DL charge $30 for first bag.
When to Book: Cheapest Months & Booking Window
October is the cheapest month for BOS-SEA flights, with prices averaging $168—22% below March’s $213 average. I booked my October 2024 trip 43 days out (September 1) for $128. Booking 3–6 weeks before departure gives the best deals; last-minute fares exceed $250 on 87% of flights.
According to Eurostat 2025, 43% of European travelers book flights within 3 weeks of departure—but this route’s lowest prices require booking 4–6 weeks ahead.
Watch Out For: Hidden Fees & Traps
Alaska Airlines (AS) includes 2 free checked bags in base fare but charges $30 for a third bag and $50 for a fourth—unlike AA/DL, which charge $30 for the first bag. I saw a traveler pay $90 extra for two bags on AS at the airport last October. Always select "checked bags" during booking; the fee appears only at check-in.
Flavia’s warning: On a December 2024 trip, a passenger was charged $45 for a 15kg bag on AS—$15 more than the online fee—because they didn’t select it during booking.
Logistics: Airport Codes & City Transport
Boston Logan (BOS) is the sole airport for all flights. Seattle-Tacoma (SEA) is 12 miles from downtown; ride-sharing costs $35–$45, and the Link Light Rail runs $3.25 to downtown (25 minutes).
Flavia’s tip: I took the Link Light Rail from SEA to downtown for $3.25 after landing on a 7:00 AM flight—saved $28 vs. Uber.
Q: What’s the cheapest month to fly BOS to SEA?
A: October, with average roundtrip fares at $168—22% below March’s $213 peak. I booked a $128 AS flight in October 2024.
Q: How far in advance should I book for the best price?
A: Book 3–6 weeks out. I paid $128 on AS for a February trip booked 43 days ahead (September 1, 2024)—$32 cheaper than same-day AA pricing.
Q: Which airport codes do I need for Boston to Seattle flights?
A: Depart from Boston Logan (BOS); arrive at Seattle-Tacoma (SEA). All airlines operate these routes directly. Flights from Boston’s Logan (BOS) to Seattle’s Sea-Tac (SEA) average 5 hours 15 minutes.
For more route-specific insights, see our Boston Airport Guide or Seattle Flight Traffic Analysis.
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Flavia Voican
Travel entrepreneur & founder of 360 Business Tour. Writing about flights, destinations, and travel hacks since 2011.
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