A turboprop engine is a variant of a jet engine that has been optimised to drive a propeller. Turboprop equipped aircraft are very efficient at lower flight speeds (less than mach 0.6), burning less fuel per seat-mile and requiring significantly less runway for takeoff and landing than a turbojet or turbofan powered aircraft of the same size. When the aircraft is used over relatively short distances, these cost and performance benefits offset the lower speed making turboprops the engine of choice for most commuter aircraft. Examples of turboprop powered aircraft include the Bombardier Dash 8, the Alenia ATR 42 and the Pilatus PC-12.