whereas although the first generation of turbofan airliners used low-bypass engines, their high noise levels and fuel consumption mean they have fallen out of favor for large aircraft. High bypass engines have a much larger fan stage, and provide most of their thrust from the ducted air of the fan; the engine core provides power to the fan stage, and only a proportion of the overall thrust comes from the engine core exhaust stream.

Over the last several decades, there has been a move towards very high