The applied aerodynamics analysis of transport aircraft still poses high challenges on the capabilities of numerical simulations. In past years, this series of STS focused specifically on the high-lift regime, where the demand on accurately predicting stall onset achieved to a sophisticating level Nowadays, new challenges arise with the progress on active flow control technologies and load control as well as new types of propulsion. This issue of the STS is intended to provide insight into such activities tackling the improvement of simulation capabilities for complex aircraft configurations, as there are: • low-speed assessment of different propulsion concepts • unsteady active flow control for load alleviation; • simulation of strut-braced wing aircraft; Contributions are coming from running international research projects governed by EU funded Research and Innovation Actions, contributions to CleanSky 2 and Clean Aviation Joint undertakings, as well as other national and international cooperation activities.