These are 5 position alpha-numeric codes comprising the d series. All other level II codes and descriptors are approved and maintained jointly by the alpha-numeric editorial panel (consisting of CMS, the Health Insurance Association of America, and the Blue Cross and Blue Shield Association).
Alaska: Although Alaska enjoys a high volume of aurora activity, its cruises are not often mentioned as northern lights cruises. During the Alaska cruise season, it's rarely dark enough for the lights to be visible.
Few places promise darker skies -- where northern lights shine brightest and dance longest -- than cruise ships sailing the Arctic Circle in winter. Northern lights cruises sail mostly the northern coast of Norway, and some venture to Iceland and Greenland. Passengers see snow-smothered fishing villages with buildings painted in primary colors, bustling commercial ports and austere, monochromatic tundrascapes.