Control line flying
Before the advent of affordable radio control systems (starting in 1937, dominant by the 1970's), aeromodelling was centered around three areas: realistic non-flying scale construction, free flight models, and control line flying. Control line flying uses a controller at the center of a sphere-shaped empty space cleared for flying. The controller holds a length of wire/string attached to a spool, and on the other end a second person launches the plane flying perpendicular to this line. The plane is guided through a series of aerobatic maneuvers (twisted to fit on the spherical flying surface) by the controller's differential pull on the wires.