X-Plane 9.70+ Saunders-Roe SR.53. The Saunders-Roe SR53 was a British prototype interceptor aircraft of mixed jet and rocket propulsion developed for the Royal Air Force by Saunders-Roe in the early 1950s. Although its performance was promising, the need for such an aircraft was soon overtaken by surface-to-air missile development and the project was cancelled after 56 test flights. Two aircraft were built and flown; one was destroyed during flight testing in June 1958. The first prototype is preserved and on public display at the Royal Air Force Museum Cosford. By Vasco Ribeiro.