Building a sustainable and climate neutral future for aviation is an inevitable requirement for a society with increasing mobility needs. If we are to stabilise the global temperature below the 1.5°C threshold set by the Paris Agreement, rapid action is to be taken. MINIMAL will contribute to a radical transformation in air transport by providing disruptive ultra-efficient and low-emission technologies that will, in combination with the aviation ecosystem, sustainably reduce the climate impact of aviation. The MINIMAL project will, through an unprecedented effort between European engine OEMs, world leading atmospheric physics scientists, and lead researchers in combustion and propulsion, attack the major sources of non-CO2 and CO2 emissions in aeroengines. This will be accomplished with the introduction of climate optimised new propulsion systems based on composite cycle engine technology, that provides unparalleled flexibility with respect to operations, and that has the potential to eliminate the large sources of effective radiative forcing by 2035: 80% reduction from contrails, 52% reduction from net-NOx, and 36% fuel burn reduction resulting in 36% to 100% CO2 reduction, depending on the fuel used. Results will allow assessing the interdependencies between non-CO2 and CO2 effects already during the early stages of aero-thermal-mechanical design and converge into engine options that have minimum climate impact. The findings are supported by numerical (TRL 2) and experimental (TRL 3) proof of concept of Low-NOx opposed-piston constant volume combustion technology with pre-micromixing of hydrogen. In MINIMAL we understand the urgency and aim for maximum impact. Aggressive, but realistic roadmaps will be outlined together with regular exchanges in major industry research centres to develop these technologies into products and bring them to in 2035-2040.