Delta Air Lines' launch of its third European route from Seattle - to London Heathrow - forms part of a concerted drive to establish the Washington state airport as a major US West Coast hub over the next three years.

The Seattle-Heathrow route joins existing Delta services to Paris and Amsterdam, and the hub will be bolstered this summer when new flights to Seoul and Hong Kong join the network starting on 2 June. Delta already serves Tokyo (both Narita and Haneda), Beijing and Shanghai from Seattle.

“We are making Seattle our West Coast hub to serve the Pacific,” says Delta’s vice president for Seattle, Mike Medeiros. “Our focus is on the transpacific. We are looking at the top business markets with a focus on Asia.”

Delta will operate 79 daily flights to 25 destinations from Seattle this summer and aims to ramp up the network over the next three years, says Medeiros. “The summer 2015 plan is 110 daily flights, 125 from 2016 and 150 plus from 2017.”

Medeiros says that “a good bit” of the planned expansion will be on new US domestic routes alongside new international destinations. Key US markets being targeted are Alaska, Hawaii and points down the West Coast. This will be to generate domestic feed for the international flights.

The expansion at Seattle could impact Delta’s relationship with Alaska Airlines, which Medeiros says is a “really good” local partner. Delta’s Seattle traffic currently comprises roughly a third origin and destination passengers, a third Delta transit passengers and a third feed generated by Alaska Airlines.

Medeiros expects that the Alaska Airlines portion will diminish over time as Delta expands its domestic markets from Seattle. “We need to feed 2,500 international seats a day and we’re going to create some feed of our own for our international hub,” he says. However he adds that “competition is good and the relationship with Alaska is good”.

Although Seattle ranks fifth among Delta’s US hubs after Atlanta, Minneapolis, New York and Detroit, it is the airline’s fastest growing, says Medeiros.

Story updated to correct planned number of daily flights.

Source: Cirium Dashboard