In today's increasingly sophisticated simulation world, a realistic, high intensity, task-loaded display of the battlespace environment has become the expectation of the military user community. To effectively train aviation aircrews, the visual system must support realistic collective/combined arms training with the required fidelity to fly nap-of-the-earth (NOE) or conduct multi-ship operations. Meeting this high level of expectations requires that the visual system be capable of performing all necessary collective tasks and supporting individual tasks with no negative training transfer or physical impacts on crewmembers. An evolving technology that can meet these needs is the Head-Mounted Display (HMD). This paper will address the use of HMDs in aviation simulators and will follow the evolution of the SIM EYE XL 100A from its early Wide Eyeâ„¢ stage, to its current use in the Army's Aviation Combined Arms Tactical Trainer - Aviation (AVCATT-A) Reconfigurable Manned Simulator program. Finally, it will address possible future improvements that can be incorporated into the HMD to further satisfy Army aviation users.