Cheap flights from London to Seattle from £377

The cheapest month to fly to Seattle from London is in February. Flight prices, which tend to average around £477, are often lower during this time because this is during the off-season. The month of January is another great option to travel to Seattle, with average flight prices from London averaging around £491.

According to our data, Thursday is the cheapest day to fly to Seattle from London. The lowest ticket price found for a Thursday departure recently was £594. Keep in mind that prices can always vary depending on your route and whether or not you are flying domestic or international. Be sure to avoid booking your departure on a Sunday as prices are generally higher than usual. According to our data, the average ticket price to Seattle on Sunday is £671.

According to our data, the cheapest time of day to fly to Seattle is at midday. momondo users have found flights departing from London to Seattle at midday for as low as £571. Keep in mind that these prices may fluctuate based on what airline you choose and the time of year you plan to travel. Flights in the morning are often more expensive, with an average ticket price of £628.

Fly from London Heathrow to Seattle/Tacoma Intl for the best London - Seattle/Tacoma Intl flight prices

You are more likely to see cheaper flights to Seattle from London when booking weeks ahead of your departure date. In general, you can expect to find flights to Seattle for around £581 when searching weeks before you fly. However, flight prices might be lower outside of this timeframe. For example, people recently found flights to Seattle from London for as low as £520 on momondo.

There are 4 cabin classes available to choose from on London to Seattle flights. Cabin price and availability will vary by airline so perform a search above to find the right deals for you.

You could potentially save up to 38% on your flight if you consider stops on a London to Seattle flight.

As of August 2026, prices for London to Seattle flights are approximately 31% cheaper when compared to flights at the same time last year.

Alaska Airlines, British Airways, and SWISS are the most popular carriers operating from London to Seattle/Tacoma Intl

Virgin Atlantic, British Airways and Alaska Airlines are the top three most popular airlines that fly to Seattle from London according to our data. Virgin Atlantic is the first choice among our users, with 52% of people opting to fly with this airline when travelling to Seattle. Keep in mind that there are 12 different airlines that fly to Seattle on a routine basis, so you have a few additional options to choose from.

Historically, on average around 11% of flights between London and Seattle have experienced a delay on any given week. The average delay length over the past 12 months has been 130 minutes.

Generally, flights departing in the evening tend to experience fewer delays. Flights departing in the early afternoon have, in the past, seen delays more frequently in comparison.

Thursday is statistically the day of the week that experiences the fewest delays on this flight route. Tuesday has historically seen more delays on average compared to the rest of the week.

According to our data, Delta have had the fewest delays on this route over the last 12 months, with about 5% of their flights experiencing any sort of delay.

Reykjavik (KEF) was the most common stop: 47% of momondo users choosing one-stop flights on this route connected there.

Flights via Munich (MUC) offer the lowest average return price of £363.

Flights connecting via Reykjavik (KEF) have the shortest average one-way travel time: 12h 58m.

Reykjavik (KEF) has the shortest average stopover time for this route: 1h 25m.

The number of flights available between London and Seattle is 21 per day as of August 2026. The most frequent departure time is 09:00, with 53% of daily flights leaving in the afternoon.

The number of flights available between London and Seattle is 151 per week as of August 2026. The most frequent departure day is Mon, with 16% of weekly flights leaving on this day.