The Majestic America Line, specializing in river and coastal cruising, has opened offices in Seattle. The newly formed line is operated by Ambassadors Cruise Group LLC, a subsidiary of Ambassadors International Inc. of Newport Beach, Calif. Majestic will have a staff of roughly 800, though only about 50 of them will be based in the line's headquarters at Fourth Avenue and Blanchard Street, company officials said.. The group was formed by merging Portland-based America West Steamboat Co., which was acquired in January, and New Orleans' Delta Queen Co., bought in April. It is expected to provide 75 percent of the annual revenue for Ambassadors International, which also operates a travel-and-events division and a marine-services division.