The First Commercial U. S. Transports

The first contracts for commercial jet transports in the United States were signed in 1955.24 The Boeing 707 and the initial version of the Douglas DC-8 were to be powered by a commercial version of P&W’s J-57, designated the JT3C-6. The intercontinental Boeing 720 and an intercontinental version of the DC-8 were to be powered by a commercial version of P&W’s J-75, designated the JT4A. The first contract for General Dynamics’ Convair 880 was signed in 1956. It was to be powered by a commercial version of GE’s J-79, designated the CJ805-3. All three of these commercial engines were slightly modified versions of their military counterparts, sans afterburner.25 These changes were minor, however. In effect, the military had borne virtually all the cost of developing the high performance engines that powered the first commercial U. S. transports. Two of these engines, the CJ805 and the JT3C, ended up providing the requisite high performance gas generators of the first successful turbofan engines.