(under subclass 24) Propelled aeronautical machines sustained by their buoyancy relative to the air, having also provision for sustentation by aerodynamic action on airfoils in fixed relation to the machines.
(1) Note. In this subclass the machines are primarily lighter-than-air craft with the fixed sustaining airfoils providing additional sustentation.
(2) Note. Machines which are primarily airplanes but have provision for carrying some lighter-than-air gas to diminish their weight are found in this class, subclass 5.
