Cheap flights from Seattle to London from $375

The cheapest month to fly to London from Seattle is in January. Flight prices, which tend to average around $641, are often lower during this time because this is during the off-season. The month of October is another great option to travel to London, with average flight prices from Seattle averaging around $647.

The cheapest day to depart from Seattle to London is on a Wednesday. Travelers who choose to depart for London on a Wednesday will often find tickets for as low as $776. If your travel schedule is flexible, try to avoid departing on a Friday because tickets tend to average around $880. These prices are subject to change though, so be sure to set up a Price Alert for flights to London.

Flying to London from Seattle at noon is the least expensive time of day to depart. momondo users have found prices as low as $820 when looking at flights departing at noon. Flights to London are more costly in the afternoon, with an average ticket price of $841. Departure times in the afternoon fall within the peak daily travel times, which is why tickets can be more expensive.

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

You are more likely to see cheaper flights to London from Seattle when booking weeks ahead of your departure date. In general, you can expect to find flights to London for around $774 when searching weeks out. However, flight prices might be lower outside of this timeframe. For example, people recently found flights to London from Seattle for as low as $674 on momondo.

There are 4 cabin classes available to choose from on Seattle/Tacoma Intl to London 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 16% on your flight if you consider stops on a Seattle to London flight.

As of February 2026, prices for Seattle to London flights are approximately 17% more expensive when compared to flights at the same time last year.

Icelandair, Lufthansa, and WestJet are the most popular carriers operating from Seattle/Tacoma Intl to London

British Airways, Delta and Virgin Atlantic are the top three most popular airlines that fly to London from Seattle according to our data. British Airways is the first choice among our users, with 35% of people opting to fly with this airline when traveling to London. Keep in mind that there are 14 different airlines that fly to London on a routine basis, so you have a few additional options to choose from.

Historically, on average around 16% of flights between Seattle and London have experienced a delay on any given week. The average delay length over the past 12 months has been 123 minutes.

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

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

According to our data, Virgin Atlantic have had the least number of delays on this route over the last 12 months; with about 6% of their flights experiencing any sort of delay.

Reykjavik (KEF) was the most common stop: 77% of momondo users choosing 1-stop flights on this route connected there.

Flights via Vancouver (YVR) offer the lowest average round-trip price of $634.

Flights connecting via Dublin (DUB) have the shortest average one-way travel time: 11h 55m.

Dublin (DUB) has the shortest average layover time for this route: 2h 05m.

As of February 2026, 11 flights take off from Seattle and land in London each day. The most common flight departure time for this route is 6:00PM, with 53% of daily flights taking off in the evening.

81 flights are operational weekly from Seattle to London as of February 2026. The most popular departure day for this route is Mon, with 15% of flights per week taking off on this day.