The objective for ICA A is to design, analyse, and evaluate alternative transition pathways in order to achieve long-term development goals for the ATS. The assessment will be based on a scientifically sound development and application of a multi-method mix, integrating scenario analysis, multi-scale modelling and simulation, life-cycle engineering, noise assessment, as well as multi-criteria and robust optimisation. Methods are developed to enable the design of a basket of technological, operational, and legislative measures on the level of single technologies, aircraft, and airports. Finally, they will allow for an assessment of effectiveness and efficiency of the complete ATS related to the achievement of economic, ecological, and social goals.