"The ATAAC project aims at improvements to Computational Fluid Dynamics (CFD) methods for aerodynamic flows used in today’s aeronautical industry. The accuracy of these is limited by insufficient capabilities of the turbulence modelling / simulation approaches available, especially at the high Reynolds numbers typical of real-life flows. As LES will not be affordable for such flows in the next 4 decades, ATAAC focuses on approaches below the LES level, namely Differential Reynolds Stress Models (DRSM), advanced Unsteady RANS models (URANS), including Scale-Adaptive Simulation (SAS), Wall-Modelled LES, and different hybrid RANS-LES coupling schemes, including the latest versions of DES and Embedded LES. The resources of the project will be concentrated exclusively on flows for which the current models fail to provide sufficient accuracy, e.g. in stalled flows, high lift applications, swirling flows (delta wings, trailing vortices), buffet etc. The assessment and improvement process will follow thoroughly conceived roadmaps linking practical goals with corresponding industrial application challenges and with modelling/simulation issues through “stepping stones” represented by appropriate generic test cases.The final goals of ATAAC are:• to recommend one or at most two “best” DRSM for conventional RANS and URANS;• to provide a small set of hybrid RANS-LES and SAS methods that can be used as “reference” turbulence-resolving approaches in future CFD design tools;• to formulate clear indications of areas of applicability and uncertainty of the proposed approaches for aerodynamic applications in industrial CFD.Contributing to reliable industrial CFD tools, ATAAC will have a direct impact on the predictive capabilities in design and optimisation, and directly contribute to the development of Greener Aircraft."