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Interestingly, while unclassified investments in engine technology are currently being chiefly driven by the Air Force, the Navy's future fighter engine budget remains classified. However, the F-35 fighter aircraft has become increasingly influential, as it is powered by the F-135 engine and represents a significant portion of both the Navy's and Air Force's tactical air fleets.
Both services are advancing separate future fighter programs under the umbrella of Next Generation Air Dominance (NGAD) initiatives. The Air Force's version will utilize engines from the Next Generation Adaptive Propulsion (NGAP) program, which promises to merge the fuel efficiency of high-bypass turbofans common in commercial aviation with the high-performance demands of military aircraft.