The invention of the helicopter was a gradual process involving many inventors, but Igor Sikorsky is widely credited with inventing the first successful modern helicopter in 1939. Earlier attempts by others included the French Breguet brothers and Paul Cornu in 1907 who achieved brief tethered and free flights, as well as steam-powered models by Gustave de Ponton d'Amécourt in 1861 and others, but these had limited success. Sikorsky's work culminated in a practical, controllable helicopter that became the basis for future developments in vertical flight.