Delta Air Lines is adding another destination in its campaign to enlarge its share of Sea-Tac Airport traffic at the expense of its local partner, Alaska Airlines.
The Atlanta-based carrier has filed schedules this week that it plans to fly from Sea-Tac to Alaska's capital city, Juneau, beginning next June.
Alaska has enjoyed a monopoly for years on the route.
The once-daily flight will operate only during the busy summer months from June 1 through August 23.
Juneau is the third Sea-Tac-Alaska route Delta is flying against Alaska Airlines. It previously has said it will fly from Sea-Tac to Anchorage and Fairbanks.
Delta in recent months has expanded its planned Sea-Tac routes to include most of Alaska's bread-and-butter West Coast destinations including Los Angeles, San Francisco, San Diego, Portland, Vancouver and Las Vegas.
Alaska and Delta remain partners, listing some of each other's flights on their schedules as their own. The two airlines have also been partners in awarding frequent flier miles to members of each other's frequent flier programs.
Delta has made no secret of its intentions of enlarging its share of the Sea-Tac market where it already ranks second to SeaTac-based Alaska.
Delta is transforming Sea-Tac into its West Coast hub for international operations. It already connects Sea-Tac with Beijing, Shanghai and both Tokyo airports along with Amsterdam and Paris in Europe.
Next year, Delta plans to add flights from Sea-Tac to Hong Kong and Seoul and to London.