Integration of Directed Energy Weapons (DEW) into future aircraft presents significant challenges. Principally, the need for generating and managing copious amounts of power into the Megawatt class is foreseen. Probably, the most critical and challenging area for supporting a DEW system on an aircraft is the Megawatt Class Electric Power System (MCEPS) and its associated Thermal Management Systems (TMS). MCEPS converts the aircraft fuel’s chemical energy into useable power for the load or system and the TMS disposes of the waste energy, all within the extremely challenging constraints (volume, weight, EMI, etc.) For the purposes of our studies, the MCEPS consists of the following subsystems: Engine, Power Generation, Power Conditioning, Distribution, Control, and Protection. The TMS manages Component Heat Extraction, Thermal Energy Storage, and Waste Heat disposal. Using a systems engineering process of analyzing requirements, defining candidate architectures, optimizing and evaluating alternatives, and verifying the system solution ensures that the potential MCEPS design solutions are traceable back to requirements based on a specific application. The MCEPS requirements analysis process evaluates various aircraft missions to identify basic requirements such as power type, quantity, quality, duty cycles, and application constraints for proper integration. These basic MCEPS design parameters drive the design options and solutions. Potential candidate architectures for power generation include: Advance secondary batteries, fuel cells, APUs, engine driven generators (conventional/low duty cycle, & super conducting), for power conditioning: Linear or active converters, for distribution, control, and protection: AC or DC, Low or High Voltage. TMS architecture candidates include; for component heat extraction: single phase, mixed phase, and two phase, and for waste heat disposal: open cycle and closed cycle. This paper discusses the pros and cons for these various approaches and the need to consider integration impacts in an application during the MCEPS design work.