Back in 1977, I was in college for my teaching degree. I was doing my teaching "internship" at a middle school in Plymouth, Michigan. One of our outings as group was to Brighton Recreation Park in Brighton, Michigan, northwest of Plymouth. It was winter and we stayed in the cabins. On our first full day, a guide took us around the camping grounds talking about it's history. The most fascinating revelations is how/why there were different types of trees surrounding the area.
He proceeded to tell us how during WWI, German migrants who arrived in the states secretly began planting various types of trees from New York, through Canada and further west of Wisconsin. As the trees matured over the decades, they became arrows, as seen from the skies, leading to factory and manufacturing sites in the different states. The strategy was for Nazi bombers to easily fly the routes and bomb these sites. Fortunately, somehow, whether seen by pilots or someone giving away the secret(s), the trees were destroyed, taken down preventing Nazi flyers from completing their missions.
I bring this up after reading about the Junker bombers and the claims of at least 1 of them making it to Michigan and New York.