In conjunction with the Air Force Institute of Technology (AFIT) and the Air Force Research Laboratory (AFRL), the University of Michigan has designed and is currently building a remotely piloted aircraft (RPA) experimental high altitude long endurance (X-HALE) aircraft to collect non-linear aeroelastic data to validate HALE aircraft design codes developed by academia, industry, and the federal government. While X-HALE is representative of HALE aircraft, the manufacturing and evaluation techniques are applicable to larger full size HALE aircraft such as the concepts being developed under Defense Advanced Research Projects Agency’s (DARPA’s) Vulture program. This paper documents the development of the X-HALE model to date including a history of the programmatic decisions, basic model configuration, geometric considerations, sensor and system architecture, and manufacturing challenges. Lessons learned from the prototyping include the evolutionary growth of X-HALE’s joiner blocks and the manufacturing process of the composite wings. Furthermore, late in the design process, a series of aeroelastic simulations using the Nonlinear Aeroelastic Simulation Toolbox (NAST) developed at the University of Michigan demonstrated the need for a rotating vertical/horizontal stabilizer to aid in the recovery of the vehicle from unstable nonlinear coupled lateral dynamic dutch roll like motion. The documentation and development of X-HALE is critical to the programmatic goal of providing a complete nonlinear aeroelastic data set for the validation of nonlinear aeroelastic analytical tools for government, industry and academia.