In this paper, we analyze different methods for assessing aerodynamic performance of air vehicles with a high degree of propulsion-airframe integration. High-speed CFD calculations of the performance of the D8 commercial aircraft concept yield a flow field data set with which to assess the different methods. A thrust-and drag-based approach is contrasted with a power-based approach to examine the similarities, differences and advantages and disadvantages to each approach. The results show both the power-based approach and an ideally expanded momentum approach offer potential to provide useful insight into the physical mechanisms driving the aerodynamic performance of integrated concepts. Based on the analysis, we also present a procedure for accounting for the impacts of integration on vehicle system-level performance, including appropriate interactions between vehicle aerodynamic and propulsion system thermodynamic performance.