Planes as big as the 747 needed high-bypass turbofan engines. High-bypass turbofans can produce twice the power of turbojets, and also use a lot less fuel. General Electric made the first of these engines. However, it was making the engines for the C-5 Galaxy. It did not make engines for airliners until later. Pratt & Whitney was also working on this type of engine. In 1966, Boeing, Pan Am and Pratt & Whitney designed a new engine, the JT9D, for the 747.