Tickets will go on sale in the autumn once regulators approve the route, which the carrier hopes to begin operating in spring 2026.
Alaska Airlines’ oneworld alliance partner British Airways already flies the Seattle route, as does SkyTeam’s Delta and its partner Virgin Atlantic.
Seattle is popular with cruise passengers, who use the city’s terminal to embark on northward itineraries.
Alaska Airlines’ flight will also open up more of the US west coast for UK travellers.
Despite its name, Alaska Airlines’ main base is in Seattle, although it has a smaller hub in Anchorage, Alaska’s capital.
