The Pratt & Whitney JT9D engine was the first high bypassratiojet engine to power a wide-body aircraft. Its initial application was the Boeing 747-100, the original "Jumbo Jet". It was the company's first high-bypass-ratio turbofan and also the first of today's generation of large commercial turbofan engines to be produced.
The JT9D was developed as part of the design phase of the C-5 Galaxy. A contract was awarded to Pratt & Whitney to study the type of large engine needed, but the production contract was eventually awarded to General Electric and their TF39 turbofan. The JT9D was, however, chosen by Boeing to power the 747, with that aircraft's first flight taking place on 9 February 1969. Flight testing of the engine had begun in June 1968, using a Boeing B-52E as a testbed.
The JT9D-3, which entered service in 1970, was constructed using titanium and nickelalloys. The engine featured a single stage fan, a three stage low pressure compressor and an eleven stage high pressure compressor coupled to a two stage high pressure turbine and four stage low pressure turbine. This version of the JT9D weighed 8,608 lb (3,905 kg) and produced 43,500 lbf (193,000 N) thrust. Production ceased in 1990.