Between June 1, 1947 to July 31, 1947, there were over 850 UFO sightings in the United States. These disks and orbs scanned the United States atomic weapon supply chain, major military bases, and radar installations.  This Summer Wave of 1947 was the most significant alien military operation incursion ever. The machines canvassed the US using the railroad lines as a form of guidance. The strategy the machines used to prioritize the sites visited was a deliberate method to create a sense of doubt about their existence and their intentions. 

These machines were autonomous alien machine drones. They operated with impunity. 

In the end, regardless of my speculation, the routes that these machine disks used is accurate and it will stand the test of time.