Aircraft modeling and simulation have become increasingly important in the areas of pilot training, safety and aircraft design, especially for unmanned aerial vehicles (UAVs). A userriendly, easily expandable, nonlinear six degree-ofreedom aircraft simulator for the Xipiter X-2C Xawk UAV was created to address these issues. The simulator will allow pilots to have an opportunity to train and gain experience in flying the aircraft even before it leaves the ground. In addition, it will allow for design modifications or new aircraft designs to be evaluated before time and money are spent on their implementation. This work can also serve as the basis for the development of control systems for the aircraft, such as a control augmentation system or autopilot.