(under subclass 4) Aeronautical machines sustained by the reaction to the downward movement of restricted masses or jets of air or other fluid. The forward propulsion of the machines may also be derived from the movement of the same or similar masses or jets of air or other fluid.
(1) Note. For machines having fixed sustaining airfoils as well as means for fluid sustentation, see this class, subclasses 12.1+.
(2) Note. For airplanes, fluid propelled, see this class, subclass 15.
(3) Note. For lighter-than-air craft partially sustained by fluid reaction, see this class, subclass 29.
(4) Note. For fluid propulsion and sustentation devices, per se, see this class, subclasses 73 and 74.
