|It has been theorized that ETI's first established a regular pattern of interaction with certain German scientists in the mid-1930's. A number of these scientists left their homeland shortly after the Nazis took power. Many immigrated to the United States and were employed by the U.S. military's Project Rainbow.
Throughout the war ETI craft were frequently sighted pacing Allied bombers and smaller aircraft over European cities and landscapes. At first the Allied pilots feared that the fierce Nazi war machine had perfected manned rocketry, but when the strange saucer-shaped objects made no hostile moves toward them, the Yanks and the Brits dubbed the things "Foo Fighters".