Perhaps the most significant change of the A300B was that it would not require new engines to be developed, being of a suitable size to be powered by Rolls-Royce's RB211, or alternatively the American Pratt & Whitney JT9D and General Electric CF6 powerplants; this switch was recognized as considerably reducing the project's development costs. To attract potential customers in the US market, it was decided that General Electric CF6-50 engines would power the A300 in place of the British RB207; these engines would be produced in co-operation with French firm Snecma. By this time, Rolls-Royce had been concentrating their efforts upon developing their RB211 turbofan engine instead and progress on the RB207's development had been slow for some time, the firm having suffered due to funding limitations, both of which had been factors in the engine switch decision.