Addressing the increasingly urgent need for sustainable aviation solutions, this study explores operational innovations as a quicker and more scalable addition to novel zero-emission propulsion systems. Through the use of regression-based causal inference methods, this study aims to understand the relationship between flight fuelburn inefficiency and the factors causing these inefficiencies. Such an approach allows for the attribution of inefficiencies to factors on an overall scale, requiring less specific domain knowledge for initial results. A case study, involving a sample of 100,000 flights, representative of European operations, reveals that airspace structure (3.2% increase in inefficiency) and turbulence along the flight plan (2.5% increase) are the leading causes, while variations in average airspeed, congestion, and crosswind contribute the least to flight inefficiency. A compilation of the results shows that the performed analysis leaves 61% of the observed flight inefficiency unaccounted for. Future work would include the exploration of different metrics even closer to actual climate and air quality effects, as well as detailed uncertainty quantification. The developed flight inefficiency prediction model allows experimentation with counterfactual scenarios, contributing to the global transition towards more sustainable air transport networks.

In this work the possibility for use of the satellite remote sensing instrument TROPOMI to detect NOx emissions from en-route aviation is assessed. Analysis of aviation intensity, quality of satellite retrievals, and emissions from non-aviation anthropogenic sources showed that the North Atlantic, including the North Atlantic Flight Corridor, would have high detection potential. Over this corridor, emissions from telemetric observed aircraft are computed under assumption of stable meteorology leading to an upper bound for the average accumulation of emissions for the months of April 2020 and April 2021. These emissions are compared with TROPOMI NO2 observations retrieved over all sky and cloudy sky scenes. In order to reduce advection influences, TROPOMI measurements at locations of aviation observations close to the overpass time are analysed separately.

General conclusions of this first assessment are not optimistic for detection of en-route aviation emissions by means of TROPOMI observations. The maximum NOx emissions attributable to en-route aviation over the North Atlantic Flight Corridor during April 2020 and April 2021 were found to be lower than detection limits associated with TROPOMI for NO2 retrieval. Neither did inspection of TROPOMI measurements at locations of recent aircraft observations retrieve any evidence of aviation-attributable emissions. Therefore detection, documentation and quantification of actual NOx emissions from en-route aviation remains a
challenge.