Delta Air Lines is launching a non-stop daily service between Heathrow and Seattle from March 2014.
The route will be operated by a 210-seat Boeing 767-300ER aircraft featuring 35 full flat-bed seats in business, 32 seats in premium economy and 143 economy seats.
The outgoing flight departs Seattle-Tacoma International Airport at 18.40 and arrives at Heathrow at 12.05 the following day.
The return service leaves Heathrow at 12.20 and arrives at Seattle at 14.40 on the same day.
Currently, only British Airways flies on the Seattle to London route with a daily service which codeshares with joint business partner American Airlines and sister carrier Iberia.
Earlier this month, Delta and Virgin Atlantic began a codeshare agreement across 108 routes in North America and the UK.
Glen Hauenstein, a Delta executive vice president, said: "Our international expansion in Seattle is possible because of our partnerships with Alaska Airlines, Virgin Atlantic Airways and Air France-KLM.
"Together the airlines can provide customers in the Pacific Northwest with an unmatched global network and an industry-leading customer experience on the ground and in the air."
Tickets for the route, which starts on March 29 (March 30 for the return service), will be available to purchase from July 27.
delta.com