There is a large number of design options to consider when designing aircraft vehicle systems for fighter aircraft, and there is a lack of tool support that provides an overview of these available design options. Various design options will bring consequences in terms of weight, performance, cost, etc. which is desired to be known in an early conceptual phase. Conventional methods, such as morphological matrix and design structure matrix, lack the ability to generate an overview and map complex systems. By studying model-based tools in form of ontologies and feature models in Protégé and FeatureIDE respectively, these tools are considered to provide a higher level of detail regarding the available design options compared to the conventional methods, such as the morphological matrix and the design structure matrix. Ontologies and feature-models are therefore considered to increase the effectiveness in the conceptual design phase of aircraft vehicle systems. By combining ontologies and feature models, more thoughtful design decisions can be performed. An increased knowledge of the available design options can lead to an improved development of aircraft vehicle systems, and new solutions can be evaluated. By performing more detailed trade studies for an unmanned aerial vehicle, for different system solutions, various parameters such as engine power outtake, system weight, etc. can be analysed and provide an indication whether a concept should be evaluated further. It is however necessary to consider how different parameters affect the overall system, and fuel penalty may be implemented as an equivalent parameter. Performing power flow calculations do however not consider solution-specific limitations, which have to be implemented to be able to determine if an aircraft vehicle system concept should be considered advantageous or not.