A Travel Air 2000 biplane made the world's first piloted flight under steam power over Oakland, California, on 12 April 1933. The strangest feature of the flight was its relative silence; spectators on the ground could hear the pilot when he called to them from mid-air. The aircraft, piloted by William Besler, had been fitted with a two-cylinder, 150 hp reciprocating engine. An important contribution to its design was made by Nathan C. Price, a former Doble Steam Motors engineer. Price was working on high pressure compact engines for rail and road transport; the purpose of the flight was to obtain publicity for this work. Following its unexpectedly favourable reception Price went to Boeing and worked on various aviation projects, but Boeing dropped the idea of a steam aeroengine in 1936. Price later worked for Lockheed where his experience with developing compact burners for steam boilers helped to design Lockheed's first jet engine. The advantages of the "Besler System" that were claimed at the time included the elimination of audible noise and destructive vibration; greater efficiency at low engine speeds and also at high altitudes where lower air temperatures assisted condensation; reduced likelihood of engine failure; reduced maintenance costs; reduced fuel costs, since fuel oil was used in place of petrol; reduced fire hazard since the fuel was less volatile and operating temperatures were lower; and a lack of need for radio shielding. For capacities in excess of 1000 horse power a turbine captures the energy released by the expansion of steam more efficiently than a piston. Thus, the steam reciprocating engine turned out to be unsuitable for scaling up to the needs of large aircraft.