The Murcian engineer Juan de la Cierva designed the autogyro — an aircraft with a free, unpowered rotor that autorotates from forward airflow, generating lift independently of fuselage speed — as a response to the frequent stall-spin accidents of airplanes of the time. The first successful flight of the Autogiro C.4 took place at Getafe on 9 January 1923. The system establishes the free-rotor principles that are the aerodynamic basis of all modern helicopters. De la Cierva died in 1936 in a commercial airliner accident at Croydon (London).