$519 Cheap Finnair flights Seattle (SEA) to London (LHR)

Grab affordable round-trip Finnair flights from $781 from SEA to LHR by sorting your results from "Price (lowest to highest)" on Expedia. Or look for options from $519 for a one-way journey.**These prices were available on Expedia within the past 7 days, for flights departing within the next year. Prices and availability are subject to change. Additional terms apply.

Look for Finnair flights from SEA to LHR about one month before you want to leave. The cheapest time to reserve an international flight is generally 18 to 29 days ahead of your travel date when you can save 17% versus booking four to five months in advance. No matter your itinerary or fare class, the best day to book international airfare is usually Sunday. Friday is often the most expensive. Passengers booking on a Sunday can save 17% on average compared to those who book on a Friday.**Ideal booking window recommendation is based on average round-trip ticket prices for January through November for 2024. Best day of the week to book recommendation is based on average round-trip ticket prices for January through October 2024. All data sourced from ARC's global airline sales database.

Sort your results by "Early Morning" and "Morning" to see the earliest flights from SEA to LHR. Taking off early means you're less likely to experience cancellations.**Most reliable time of the day recommendation is based on January through August 2024 flight status data sourced from OAG's global flight data platform.

Finnair makes flying from SEA to LHR more enjoyable with a 4-star airline rating and a rewarding loyalty program. You also have the chance to earn points with Finnair Plus. Don't forget to join Expedia's free One Key™ rewards program to earn OneKeyCash™*, which can be redeemed on future trips.*OneKeyCash™ disclaimer - OneKeyCash™ is not redeemable for cash and can only be used on Expedia, Hotels.com and Vrbo.