Concrete ideas of constructing vertical take-off and landing (VTOL) aircraft using helicopter-like rotors were pushed further in the 1930s. The first design resembling modern tiltrotors was patented by George Lehberger in May 1930, but he did not further develop the concept. In World War II, Weserflug in Germany came around 1938 up with the concept of their P.1003/1, which was tilting to the top with part of the wings but not the full wings, so it may be inbetween tilt-rotor and tilt-planes. Shortly after a German prototype, the Focke-Achgelis Fa 269, was developed starting in 1942, which was tilting to the ground, but never flew. Platt and LePage patented the PL-16, the first American tiltrotor aircraft. However, the company shut down in August 1946 due to lack of capital.