His first fixed-wing plane, the S-1 failed, because its 15-horsepower (11-kilowatt) engine was inadequate. His second plane, the S-2 was a success. His fifth plane, the S-5, won him national recognition. With its 50-horsepower (37.3-kilowatt) engine, he could stay aloft for more than an hour, reach heights of 1,500 feet (457 meters), and make short trips. He also earned pilots license number 64 from the Fédération Aéronautique Internationale. His S-6-A received the highest award at the 1912 Moscow Aviation Exhibition, and later that year, won first prize in the military competition at Petrograd. Sikorsky also began supplying aircraft to the Russian army.

His next step was to design and build the world's first four-engine plane. "Le Grand," featured innovations such as an enclosed cabin, a lavatory, upholstered chairs, and an exterior catwalk atop the fuselage where passengers could get some fresh air. His next plane was the even larger Ilia Mourometz, which was used as a bomber during World War I.

The Russian Revolution ended Sikorsky's career in Russia. He emigrated to France where he was commissioned to build a bomber for Allied service. But the war ended and Sikorsky, after searching in vain for a position in French aviation, came to the United States in 1919, determined to start his own aircraft company.

After World War I, the market for aircraft disappeared, so Sikorsky went to work as an engineer and consultant for the Army Engineering Division. He was able to attract enough funds so that in 1923 he formed the Sikorsky Aero Engineering Corporation in Long Island, New York. His first U.S. design was the S-29-A, a twin-engine transport that debuted on May 4, 1924. But the plane had too many passengers on board and it crashed, suffering extensive damage. He managed to raise some additional money and put a better engine on the S-29, which flew on September 25, 1924. It was safe and reliable and became a popular transport and cargo plane.

He still could not get government business, though, but managed to attract $1 million from an investment group. The new Sikorsky Manufacturing Corporation was formed on July 25, 1925. The new company's first design, the trimotor S-35, piloted by French ace, René Fonck, failed in its attempt to cross the Atlantic Ocean in September 1926, crashing on takeoff and killing two crew members. Shortly after, Sikorsky teamed with Consolidated Aircraft in an attempt to win a government contract for a new bomber. They lost out to Curtiss Aircraft, but this may have been the first time that two unaffiliated companies cooperated to pursue a contract.

Beginning in the late 1920s, Sikorsky finally achieved commercial success with amphibians, particularly the S-38, which first flew on June 25, 1928. Able to accommodate 8-10 passengers comfortably, the plane had an unusual structure with connecting rods joining the wings and fuselage. It had retractable landing gear and could land on either water or land. About 120 of the three S-38 models were built. In 1931, the first S-40 amphibian, the “American Clipper,” rolled off the assembly line. It was followed in 1934 by the S-42 clipper that inaugurated the first transoceanic air service and flew the first airmail from Honolulu to the mainland United States. In 1937, the S-42 made the first regular airline crossing of the North Atlantic Ocean and pioneered the transpacific route to Asia.

The S-44, the world's longest range commercial aircraft, followed in 1937. It was the only aircraft to have flown commercial scheduled service nonstop across the north and south Atlantic. The S-44 was the last fixed-wing aircraft built by Sikorsky.

Sikorsky's flying boats, however, made little money, and in 1938, United Aircraft directed Sikorsky to stop building them and gave him $250,000 for helicopter development. He would go on to make his most important contributions in the area of helicopter design. His VS-300, first built and flown in 1939, became America's first successful helicopter and introduced a new mode of military and commercial transportation. On May 6, 1941, in an improved version, he established an international endurance record of 1 hour 32.4 seconds.

Meanwhile, Sikorsky reorganized again in October 1928 as Sikorsky Aviation Corporation and moved to Stratford, Connecticut in 1929. On July 30, 1929, Sikorsky joined the United Aircraft and Transport Corporation (UATC), a large holding company. It stayed with UATC until the holding company was forced to dissolve in September 1934. It then joined with the engine company Pratt & Whitney, planebuilder Vought, and propeller-maker Hamilton Standard to form the United Aircraft Manufacturing Company. In 1939, Sikorsky and Vought united to form Vought-Sikorsky. Vought produced the F4U-1D Corsair, a single-engine plane used extensively in World War II.