SAS will seasonally fly five times per week between Denmark and Seattle, starting May 21.
Seattle will be Scandinavian carrier's 10th U.S. destination from Copenhagen, joining Atlanta, Boston, Newark, New York, Los Angeles, Washington Dulles, Chicago, San Francisco and Miami.
SAS also flies from Stockholm to Newark and Miami and serves Newark from Oslo.
The addition of Seattle, where Delta has a hub, follows SAS's recent move from the Star Alliance to SkyTeam, in which Delta is a member.
SAS will be the lone carrier flying Copenhagen-Seattle.