Sikorsky Aircraft and it became a part of [[United Aircraft and Transport Corporation]] (now [[United Technologies Corporation]]) in July of that year. [[File:Sikorsky Aircraft Corporation ad Model S-42 Clipper Flying Boat 1937.jpg|thumb|left|upright|Advertisement for [[Sikorsky S-42]] Clipper flying boat from 1937]] In the United States, Igor Sikorsky originally concentrated on the development of multi-engined landplanes and then amphibious aircraft. In the late 1930s, sales declined and United Aircraft merged his division with [[Vought Aircraft]]. He then began work on developing a practical helicopter. After first flying the [[VS-300]] he developed the [[Sikorsky R-4]], the first stable, single-rotor, fully controllable [[helicopter]] to enter full-scale
Igor Sikorsky a naturalized citizen of the United States. The Sikorsky Manufacturing Company moved to Stratford, Connecticut in 1929. It became a part of the United Aircraft and Transport Corporation (now United Technologies Corporation) in July of that year. The company manufactured flying boats, such as the S-42 "Clipper", used by Pan Am for transatlantic flights. Meanwhile, Sikorsky also continued his earlier work on vertical flight while living in Nichols, Connecticut. On February 14, 1929, he filed an application to patent a "direct lift" amphibian aircraft which used compressed air to power a direct lift "propeller" and two smaller propellers for thrust.