 1902 by the French-Swiss brothers Henri and Armand Dufaux, for which they got a patent in February 1904, and made their work public in April 1905.Conrete 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.