Cheap flights from Seattle to London from $368

The month of January is, on average, the cheapest month to fly to London Heathrow Airport from Seattle, with most prices found around $642. If you’re not able to fly to London Heathrow Airport in January, then October is your next best option. Flight prices from Seattle to London Heathrow Airport during October average around $679.

Our data shows that Wednesday is the least expensive day to fly to London Heathrow Airport. Tickets to fly out on this day can be as low as $803. The most expensive day to fly to London Heathrow Airport is Friday, with ticket prices averaging around $898.

According to our data, the cheapest time of day to fly to London Heathrow Airport is at noon. momondo users have found flights departing from Seattle to London Heathrow Airport at noon for as low as $821. 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 afternoon are often more expensive with an average ticket price of $869.

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

You are more likely to see cheaper flights to London Heathrow Airport from Seattle when booking weeks ahead of your departure date. In general, you can expect to find flights to London Heathrow Airport for around $827 when searching weeks out. However, flight prices might be lower outside of this timeframe. For example, people recently found flights to London Heathrow Airport from Seattle for as low as $727 on momondo.

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

KLM and Delta are the most popular carriers operating from Seattle/Tacoma Intl to London Heathrow

Delta, British Airways and Virgin Atlantic are the top three most popular airlines that fly to London Heathrow Airport from Seattle according to our data. Delta is the first choice among our users, with 33% of people opting to fly with this airline when traveling to London Heathrow Airport. Keep in mind that there are 13 different airlines that fly to London Heathrow Airport on a routine basis, so you have a few additional options to choose from.

Historically, on average around 14% 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 128 minutes.

Generally, flights departing at night tend to experience fewer delays. Flights in the evening 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. Wednesday 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: 87% of momondo users choosing 1-stop flights on this route connected there.

Flights via Copenhagen (CPH) offer the lowest average round-trip price of $736.

Flights connecting via Dublin (DUB) have the shortest average one-way travel time: 11h 30m.

Dublin (DUB) has the shortest average layover time for this route: 2h 35m.

As of May 2026, 20 flights take off from Seattle and land in London Heathrow Airport each day. The most common flight departure time for this route is 1:00PM, with 71% of daily flights taking off in the evening.

143 flights are operational weekly from Seattle to London Heathrow Airport as of May 2026. The most popular departure day for this route is Tue, with 15% of flights per week taking off on this day.