PSA will add flights to 6 Pacific Northwest cities.

The San Diego-based airline said it will begin non-stop service from San Francisco to Eureka, Calif.; Medford and Eugene, Ore.; Pasco and Yakima, Wash., and Boise, Ida., on Dec. 19. A flight schedule and price structure will be announced next month. The planned addition of the new cities would be the largest single expansion in the airline’s 36-year history, according to an airline spokesman.