Aviation etymology - the Blue Spruce routes

There is a set of published short-range routes across the North Atlantic, used by small airplanes that don’t have either the range or the proper equipment (or both) to make a nonstop flight between the European and North American continents. These routes use airports and ground-based navigational aides in Northern Canada, Greenland, Iceland, and Scotland. I read they were organized by ferry pilots just before (or during) WWII, and they’re known as the Blue Spruce Routes. I’m interested in the name - is it just because one spends a lot of time flying over blue spruce forests in Canada? I’ve done a bit of googling but didn’t come up with much - several people have asked on various aviation fora, but none of the ones I found got what I would consider to be a satisfactory answer.

New one to me, but I do know that the fields the USAAF built in Greenland had code names starting with “Bluie”. The Narsarssuaq airport, for instance, was originally “Bluie West One”. Dunno what the Gander, Goose Bay, and Keflavik airports, the other main links in the route along with Glasgow, were originally called, sorry.

I can heartily recommend Ernest Gann’s autobiographical Fate is the Hunter (no connection to the movie) and Guy Murchie’s *Song of the Sky *if you’re interested in the early days of the route.

No factual data on the actual etymology, but the majority of the route is either over tundra or taiga, the latter mostly spruce forest. And blue spruce is not just an interesting ornamental variant, but a very common spruce species. I grew up in a two-story-plus-full-attic double house that may have been 40-45’ high; its backyard was dominated by a blue spruce that stood significantly taller, my wife and I having independently guessed 60’ for its height just now. (It had to come down some 25 years back.)

I’ve found, so far, a 1977 newspaper article which said they were called both “blue spruce route” and the “radio route.”

Very surprisingly, you can’t find a Google Book Search hit until 2006. Truly mystifying.

I have no knowledge of the specific routes, or how they came to be named, but have a lot of experience flying airplanes with engines that failed to be include in the design. (gliders)

Flying over large heavily forested areas leaves a pilot few good options in the event of engine failure. It wouldn’t be surprising that the trees and thus lack of places to make an emergency landing were considered the most distinguishing feature of the routes by the pilots who flew them. It is very commonly noted that aircraft engines develop odd sounds when the airplane reaches a point well beyond gliding range of any desirable place to land. This is sometimes referred to as “auto-rough over water” effect.