Aviation can reduce its climate impact by controlling its CO₂-emission and non-CO₂ effects, e.g., aviation-induced contrail-cirrus and ozone caused by nitrogen oxide emissions. One option is the implementation of operational measures that aim to avoid those atmospheric regions that are in particular sensitive to non-CO₂ aviation effects, e.g., where persistent contrails form. The quantitative estimates of mitigation potentials of such climate-optimized aircraft trajectories are required, when working towards sustainable aviation. The results are presented from a comprehensive modelling approach when aiming to identify such climate-optimized aircraft trajectories. The overall concept relies on a multi-dimensional environmental change function concept, which is capable of providing climate impact information to air traffic management (ATM). Estimates on overall climate impact reduction from a one-day case study are presented that rely on the best estimate for climate impact information. Specific weather situation that day, containing regions with high contrail impact, results in a potential reduction of total climate impact, by more than 40%, when considering CO₂ and non-CO₂ effects, associated with an increase of fuel by about 0.5%. The climate impact reduction per individual alternative trajectory shows a strong variation and, hence, also the mitigation potential for an analyzed city pair, depending on atmospheric characteristics along the flight corridor as well as flight altitude. The robustness of proposed climate-optimized trajectories is assessed by using a range of different climate metrics. A more sustainable ATM needs to integrate comprehensive environmental impacts and associated forecast uncertainties into route optimization in order to identify robust eco-efficient trajectories.

Air traffic management as currently under development by the Single European Sky ATM Research program SESAR has an important role to play in reducing environmental impact of aviation by means of green trajectories, in addition to the improvements to be derived from new aircraft and engine technologies. A comprehensive modelling approach is presented which allows identifying aircraft trajectories having a lower environmental impact compared to the fuel optimal solution. Algorithmic environmental change functions are introduced which allow determining impact of aircraft emission at a given position and time from standard meteorological forecast parameters. A case study for three city-pairs is presented using reanalysis meteorological data. Mitigation potential of environmentally optimized trajectory options is analyzed, using a set of different climate impact metrics identifying robust routing options. This study presents results for a multi-criteria environmental assessment of aircraft trajectories relying on an advanced MET service as developed within the Exploratory Research Project ATM4E (SESAR2020). This framework allows studying and characterizing changes in traffic flows due to environmental optimization, as well as studying trade-offs between distinct strategic measures.