The Pratt & Whitney JT9D turbofan was developed to power the current generation of wide-body commercial jets. It first ran in 1966, was flight tested in 1968, and received FAA certification in 1969.

JT9D engines powered the Boeing 747 on its first flight on February 9, 1969, and entered airline service in 1970. The JT9D also powered some versions of the McDonnell Douglas DC-10, and Airbus Industrie A300 and A310.

An advanced design, the JT9D was the first of the very large, high bypass ratio turbofans in commercial service. The JT9D displayed here is a pre-production engine built for ground testing rather than for flight, although it is outwardly identical to production examples.