The site of Igor Sikorsky’s first successful helicopter flight, is now on the register of historic places for the state of Connecticut. The Stratford Army Engine Plant was registered as the "Vought-Sikorsky Aircraft Plant," a joint venture of the aircraft makers that built the gull-winged F4U Corsair of World War II fame. It was also the site of Sikorsky’s maiden VS-300 flight. He flew the aircraft tethered on Sept. 14, 1938, and made his first free flight May 13, 1940. From the 1920s on, the property was used for aviation and national defense manufacturing. From the Korean War on, it was controlled by the Defense Dept. and then the U.S. Army. The plant closed in 1995. State officials are offering tax credits and grants for work to preserve the buildings.