The EU EFACA project considers two conceptual aircraft design configurations for cleaning European air traffic in future decades. The EU SENECA project considered four conceptual configurations for supersonic aircraft design—it is also expected to impact air traffic in future decades. Recently, several different technologies have led to propulsion designs that have the potential to reduce greenhouse gas emissions and replace existing conventions, including jet fuel technology. On one hand, H₂-powered aviation just recently regained significant attention from the industry, e.g., Airbus launched the ZEROe program, where they pledged to develop the world’s first zero-emission commercial aircraft by 2035. On the other hand, sustainable aviation fuels or biofuels have been identified as an alternative option, also with the potential for use in supersonic flights. In both projects, the results of the assessment of environmental factors are considered using a multidimensional approach, ranging from aircraft certification requirements to regional/global assessment of new designs in air traffic. Any factor reduction technology is simulated and compared to a reference, usually the current best in its aircraft class, providing the possibility to assess its efficiency for necessary certification requirements and for real or forecasted operational conditions, in particular due to the ACARE goals assessment in mid-2035 and long-term 2050 terms.