Igor Sikorsky was a Russian-American aviation pioneer and inventor. He is best known for his pioneering work in helicopter technology, and is credited with inventing the first successful helicopter in 1939. He also designed the first four-engine airplane, the Ilya Muromets, which was used by the Imperial Russian Air Force during World War I. Sikorsky founded the Sikorsky Aircraft Corporation in 1925, which is now one of the world's leading manufacturers of helicopters. He was inducted into the National Aviation Hall of Fame in 1973.