Step and cruise climbs are not normally applicable to lower-flying aircraft propelled by conventional piston engines with propellers or turboprops, since their performance characteristics may be very different from those of turbofan or jet engined aircraft. In fact, the most efficient altitude for a small general aviation aircraft may be only some 300-1000 meters (a few thousand feet) above the ground, and increasing altitude may diminish efficiency rather than improve it (propellers tend to lose efficiency in thinner air, and many small general aviation aircraft lack supercharging, effectively decreasing the engine's compression pressure, and therefore efficiency, as the aircraft climbs into more rarified atmosphere).