By January 1944, the fuselage shell for the first prototype D.H. 103, "RR915", was under construction on production jigs at Hatfield; "RR915" was rolled out for engine runs on 20 July 1944. On 28 July 1944, only thirteen months after the official sanction to proceed with development, "RR915" conducted its maiden flight, piloted by Geoffrey de Havilland Jr., the company's chief test pilot. Flight tests of "RR915" led to it achieving a recorded speed of 485 mph (780 km/h) in level flight. Within two months, over fifty flight hours were accumulated by "RR915". The second prototype, "RR919", was more representative of production aircraft, having provision for a pair of 200-gallon drop tanks and a pair of 1,000 lbs bombs on hard points underneath the wings.