The Boeing Company has developed a mobile robotic drilling and fastening system for use in assembly processes on the lower panel of a horizontally fixtured wing. The robotic system, referred to as Lower-panel Drilling and Fastening System (LPDFS), was initially developed as part of an initiative to minimize facilities costs by not requiring costly foundation work. It is designed to operate with a high level of autonomy, minimizing operator intervention, including that required for machine setup and tool changes. System design enables positioning the work piece at a lower ergonomic height for concurrent manual processes. In all aspects of design, the system will maintain maximum flexibility for accommodating future manufacturing changes and increases in production rate, while meeting the strict accuracy requirements characteristic of aircraft manufacturing. This novel system consists of an Automated Guided Vehicle (AGV) that provides rough positioning of the robotic system in relation to the aircraft structure, a Hexapod type of Parallel Kinematics Machine (PKM) for fine positioning, and a multifunction end effector for part acquisition, drilling, hole inspection, and fastener insertion. This paper will examine the robotic system design, operation, and end effector development to date, the results of testing, as well as a discussion of the advantages of such a system for use in assembly processes.