Boeing hasn't engineered a clean-sheet commercial airplane since its cash cow 787 Dreamliner launched in 2004. The planemaker has instead opted for upgrades to already-built planes, as it was cheaper and less complicated. However, a September report from The Wall Street Journal said that Boeing was actively developing an all-new plane to replace its 737, a jet that has evolved through four generational modifications since its debut in 1967 and has largely exhausted its upgrade viability.Boeing's 737 narrow ...