This is fascinating. Have you ever heard about these early navigational aids for airmail planes that were built in the 1920’s?
The first effort at 2-day delivery. According to an article I read the other day, we will be lucky in the near future to get delivery of first class mail to our homes 3 days a week. How far the mighty have fallen!
A detailed article about the subject.




cool!
LikeLiked by 1 person
Never knew about this. Thanks.
LikeLiked by 2 people
Fascinating! I sent this on to my DIL to show the girls.
LikeLiked by 1 person