General Electric is joining with NASA to revive studies of its long-abandoned GE36 unducted fan, or "open rotor" and is simultaneously launching a next-generation CF34 technology effort as part of a pressing drive to develop families of fuel-saving engines. GE stresses that the two-pronged move, which throws down the gauntlet to Pratt & Whitney's geared turbofan (GTF) ambitions, is part of a long-term strategy that could lead to both open-rotor and advanced conventional turbofan demonstrators in the latter part of next decade. GE and NASA have signed a Space Act agreement covering studies of the open rotor concept, which offers the potential for up to 30% lower fuel burn compared with current engines. The NG34 technology plan, aimed at regional jets, has potential for up to 20% fuel savings.