America's youth builds and flies model planes on miniature flying fields. This young mechanic, equipped with a well-fitted tool kit, goes after engine trouble in his model plane. Like millions of other boys, he is vitally interested in aero-modelling, and is learning in his home workshop principles of aeronautical engineering which he will put to good use in the air-minded post-war world. Young model plane builders recently turned out 800,000 scale model airplanes for use by the U.S. Navy, the U.S. Army, and civilian defense groups to train their personnel to recognize hostile and friendly aircraft. The models, which were built in a scale of one to seventy-two, were representations of all types of aircraft used by the United Nations and the enemy