More electrically powered aircraft reveals some significant advantages such as weight decrease, reduced maintenance requirements and increased reliability and passenger comfort. However, the development of the future more-electric aircraft (MEA) systems is a very challenging task. Its complexity may be handled by a model supported design approach for the total aircraft design process. A key factor of applying model based design is dedicated modeling and simulation techniques for all design phases. The highest complexity can be seen in the systems validation and verification phase where the aircraft system is integrated from the supplier's models. While the capability to conveniently model complex physical systems with Modelica is generally accepted, the capability to perform large scale model integration and analysis as part of a validation and verification process remained unproven. In this paper we give evidence of Modelica/Dymola to be suitable for the virtual testing of complex energy systems in the future MEA design process. We demonstrate the modeling and the simulation results of component stand-alone tests as well as the tests of an integrated aircraft power network.