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.
For those who live in Alaska, the Aurora is a part of northern life. Fall, winter and spring is the special season for viewing the great lights for residents and off-season visitors. Some Alaskans have Aurora Alerts; when a display begins, the first person to spot them begins a phone tree to get the word out.