The 1960s brought new challenges, from more complex technology and bigger, more expensive aircraft to more mature markets with stiffer competition from GE, Rolls Royce, and SNECMA. The competitions for the requested aircraft that would become the Lockheed C-5 Galaxy and the Boeing 747 were some of the financially riskier episodes. Pratt & Whitney ended up building the engines for the 747, producing the Pratt & Whitney JT9D, but the program was rocky. For several years Boeing and Pratt & Whitney struggled with an aircraft that was too heavy and underpowered. Eventually, after a lot of continued development work, the 747 redeemed itself.