America's youth builds and flies model planes on miniature flying fields. This unusual model airplane, a composite of several different types, is launched by its youthful builder at Modelhaven Airport, "the smallest airport in the world," near the city of Baltimore in the eastern state of Maryland. Model building is a popular hobby among young Americans, who band together in clubs and classroom groups to turn out model airplanes of every type and variety. When the U.S. government in 1941 called on model plane builders to turn 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, it was estimated that there were nearly three million American youths actively interested in aero-modelling