The Pratt & Whitney J57 (company designation: JT3C) was an axial-flow turbojet engine developed by Pratt & Whitney in the early 1950s. The J57 ( first run January 1950[1] )was the first 10,000 lbf (45 kN) thrust class engine in the United States. The J57/JT3C was developed into the J75/JT4A turbojet, JT3D/TF33 turbofan and the PT5/T57 turboprop.[2]