A modeling and simulation based methodology is proposed to study the power flow dynamics of commercial aircraft electrical systems in the context of increasing aircraft electrification. The crucial elements of the aircraft electrical system are power sources (synchronous generators and batteries), power converters (transformers, rectifiers and inverters), and electrical loads (ac and dc). Individual components are modeled to incorporate their dynamic behavior and to interface with other components. These component models are assembled into a representative aircraft electrical system for simulation and then trade studies are performed to analyze component sizing, design architecture, fault conditions, and efficiency calculations. The developed models enable components to be scaled to various power levels. A major challenge involved in simulating extensive systems is to achieve an optimum balance between simulation time and the desired level of detail associated with the results. This work makes use of a combination of dynamical models and steady state average models based on their levels of criticality. The current modeling approach on a sample 5.3 hour flight mission has been shown to execute at a speed 4x faster than real time.