OPeRATOR project will develop the capability to analyse a digitally operational, virtually integrated aircraft with respect to realistic operational scenarios. Systems and propulsion have become some of key contributors to meeting the Flight Path 2050 goals, introducing radically new approaches to aircraft design, the integration of new technologies and further optimization of aircraft operations. The key objective of OPeRATOR is to develop modelling and simulation technologies that enable virtual validation of such technologies under highly representative operation conditions. To this end, OPeRATOR will develop a Software library that is able to (1) make a virtually integrated aircraft model fly by appropriately integrating flight physical aspects, (2) virtually operate it in a realistically modelled environment and (3) to enable the analysis of over-all and individual system behaviour during user-specified virtual missions. The software library will be implemented in the Modelica language and capabilities will be provided to interface the models developed into other analysis tools. OPeRATOR is a mono-partner proposed by DLR (DE), who has been contributing in this field and is keen to bring its competences and expertise with multi-disciplinary flight physics and systems modelling, Modelica library and language development, the Functional Mock-up Interface standard, as well as realistic mission simulation for aircraft over-all design to the project.