Aircraft Wankel engines are increasingly being found in roles where the compact size, high power-to-weight ratio and quiet operation are important, notably in drones and unmanned aerial vehicles. Many companies and hobbyists adapt Mazda rotary engines, taken from cars, to aircraft use. Others, including Wankel GmbH itself, manufacture Wankel rotary engines dedicated for that purpose. One such use is the "Rotapower" engines in the Moller Skycar M400. Another example of purpose-built aircraft rotaries are Austro Engine's AE50R (certified) and AE75R (under development) both appr. 2 hp/kg.