This paper describes plans towards a flight test of an autonomous guidance system for unmanned aerial vehicles (UAVs). The goal of the experiment, which will take place on Boeing's UAV testbed in 2004, is to demonstrate key autonomy capabilities that are critical for future UAV operations. These are enabled using a receding horizon implementation of a trajectory planner formulated as a mixed integer linear program (MILP). Hybrid vehicle dynamics combining multiple linear time-invariant (LTI) modes are used to cover the scope of vehicle dynamics. In addition to the LTI modes, coordinated maneuvers that have inherent operational value can be embedded. The planner also recognizes a number of task primitives. Trajectory safety is guaranteed by computing a rescue path at every time step. Prototype demonstration scenarios have been designed to exercise and evaluate the guidance system's primary autonomy capabilities. The paper also describes the key milestones of the technology buildup and transition to the Boeing open control platform and flight test program.