The phrase "flight shame" symbolically reflects the strong social demand for improving the environmental compatibility of aircraft. Under such circumstances, the aircraft of the future, which are to be fueled with sustainable aviation fuel (SAF) or hydrogen and are regarded as one of the most effective measures, have problems of high fuel costs and limited cruising ranges. As a means to promote decarbonization on the energy demand side toward achieving carbon neutrality, the weight reduction in airframe is getting increasingly important, because it will lead to a higher fuel efficiency and a longer cruising range. In the post-coronavirus society, on the other hand, there is growing demand for narrow-body aircraft. However, the application of composite material in narrow-body aircraft is hampered by the difficulty of reducing the weight and raising the production rate; there is, therefore, less progress being made than with wide-body aircraft in this regard. As an initiative to make a breakthrough in this situation, Mitsubishi Heavy Industries, Ltd. (MHI) has engaged in the research and development of advanced composite material technology that can realize weight reduction of future/narrow-body aircraft, under the sponsorship of the Green Innovation Fund Project by the New Energy and Industrial Technology Development Organization (NEDO) since 2021.