The plane that slammed into a mountainside near Nome in February lacked a voluntary but key piece of equipment that could have sped the rescue of the five passengers and pilot, a federal investigator said last week. Frontier Flying Service hadn’t removed the plane’s emergency beacon — a type that is no longer being heard by satellites — and replaced it with an updated model, said Jim La Belle, regional director for the National Transportation Safety Board in Alaska. The Fairbanks airline isn’t alone. Most of the state’s small commercial airlines apparently haven’t updated their equipment, though doing so is...