"Dick" writes:

Let me change that from "any thoughts" to "any helpful" thoughts G.

In his AvWeb piece on scud-running, Rick Durden mentions that the mail
pilots in the 1920's just kept flying lower until they could see the
ground, even if that meant skimming the tree-tops:

http://www.avweb.com/news/columns/182679-1.html

By the 1930's, I imagine, some of them had gyroscopic instruments.
Perhaps Rick can point us to online references.


All the best,


David