[fragmede]

Economics. Japan has chosen to specialize in other areas and being a jet turbine engine manufacturer isn't where they've chosen to put resources in. The pay off simply isn't there. They're there in the supply chain, with IHI, MItsubishi, and Kawasaki being in the business of advanced titanium and nickel superalloys being used in wind, steam, and gas turbines for powerplants. It's just that the economics of commercial jet engines themselves isn't something they've chosen to pursue.