Dan Matthews (Broderick Crawford) enlists the aid of the Civil Air Patrol, which is a congressionally chartered federally supported non-profit corporation that serves as the official civilian auxiliary of the United States Air Force. It was founded December 1, 1941, just prior to the United States entry into World War II.
The stolen airplane was an Ercoupe. Very capable of landing on a rough airstrip. Also very fun to fly, the canopy can be left open with just the windscreen for protection. There were other Ercoupes seen on the Civil Air Patrol field. The Piper Cubs, and what looks to be a Liscomb, are preferred by CAP search squadrons because of their high wing for visibility below. The Ercoupe is low-wing, but the side-by-side seating gives both pilots a forward view.