A requirement has appeared within the next generation of commercial aircraft for a modern engine of between 30,000 and 36,000 lb. thrust. The RB 211-535 meets it by extending the RB 211 family's thrust range downwards, and is based on the fully developed RB 211-22B H.P. system running derated. Its design retains the parent engine's proven advantages and provides fuel consumption and noise levels similar to the existing large fan engines. The derivative nature of the design ensures low risk development and service introduction, and low airline maintenance material costs. Overall, the RB 211-535 comes close to the optimum solution to the requirement.