The popularity and advancing capabilities of commercial head mounted displays (HMD) has opened the opportunity for the innovative application of virtual reality (VR), augmented reality (AR), and mixed reality (MR), aka extended reality (XR) devices to support Naval aviation training applications. In recent years, the US military has been looking at introducing new training methods to speed up pilot training by using a combination of XR, artificial intelligence, and modeling and simulation technologies within a new airman-training curriculum.  In theory, the near-eye displays (NED) in XR headsets are just another type of display device available for flight simulators. However, even though HMDs share similar components with traditional flight simulator displays, there are significant differences in scale and performance of these components. As a result, traditional visual display system (VDS) test equipment cannot be used to measure the performance of a fully integrated XR display system. This paper provides background on conventional Navy VDS requirements and testing methods and presents a set of preliminary HMD parameters and methodology for the evaluation of this technology within a flight simulator. This paper also presents information on the initial implementations of a set of VR test patterns as well as data collected (e.g. field of view (FOV), static resolution, and latency) for several VR headsets. Finally, the paper concludes with future research plans for the development of requirements and methodology for the evaluation of a MR HMD within a flight simulator.