Cheap flights from Seattle to London from £270

In general, January is the cheapest month to fly from Seattle to London Heathrow Airport. Due to it being the ‘off-season’ during this time, you can expect flight prices to be around £478. The month of October is another great option to travel to London Heathrow Airport, with average flight prices from Seattle averaging around £505.

On average, the least expensive day to fly to London Heathrow Airport from Seattle is on a Thursday. momondo users have found tickets for Thursday departures for as low as £524. However, this price may fluctuate depending on the airline, the season, and holidays. Be sure to avoid booking your departure on a Monday as prices are generally higher than usual. According to our data, the average ticket price to London Heathrow Airport on Monday is £653.

According to our data, the cheapest time of day to fly to London Heathrow Airport is in the evening. momondo users have found flights departing from Seattle to London Heathrow Airport in the evening for as low as £544. Keep in mind that these prices may fluctuate based on what airline you choose and the time of year you plan to travel. If you have a flexible travel schedule, then try to avoid flying in the afternoon when prices are £612 on average. Flights to London Heathrow Airport from Seattle in the afternoon are generally more expensive because this time of day is more convenient for travellers’ schedules.

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 £617 when searching weeks before you fly. 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 £539 on momondo.

There are 3 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.

You could potentially save up to 71% on your flight if you consider stops on a Seattle to London Heathrow Airport flight.

As of June 2026, prices for Seattle to London Heathrow Airport flights are approximately 11% cheaper when compared to flights at the same time last year.

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 127 minutes.

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

Saturday is statistically the day of the week that experiences the fewest 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 fewest delays on this route over the last 12 months, with about 6% of their flights experiencing any sort of delay.

As of June 2026, 22 flights take off from Seattle and land in London Heathrow Airport each day. The most common flight departure time for this route is 20:00, with 69% of daily flights taking off in the evening.

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