The determination of aircraft stability and control derivatives from wind-tunnel and computational fluid dynamics data can be an expensive and time-consuming procedure. This case study shows how linear system identification techniques can be used to obtain this information with sufficient accuracy to design a satisfactory flight control system for an aerial target of the Royal Thai Air Force. Just one flight was undertaken, using a racetrack manoeuvre, to provide the data for identification and validation. The system parameters were identified and a flight control system was designed. Hardware-in-the-loop simulation was used to perform initial tests on the controller and to test the control system hardware and software. A second flight was performed to test the resulting controller, and a satisfactory performance was obtained without the need to adjust the controller gains. This case study demonstrates how system identification techniques can be used for UAV control system design and development in a cost-effective manner. An ordinary piloted manoeuvre and off-trim condition flight data (racetrack manoeuvre) were studied and identified in order to estimate the aerodynamic coefficients of the RTAF aerial target. As shown by the flight test results of the PID autopilot, the identified 6-DOF non-linear model was sufficiently reliable and accurate for the design of a satisfactory control system. In this work, only two flight tests had to be undertaken. The first flight test was done to record flight data by controlling the aerial target manually for a flight duration of 12 min. The second flight test was done to validate the PID autopilot for a flight duration of 26 min. However, both flight tests were performed in one flight condition; it is envisaged that gainscheduling will be required to cover a fuller range of flight conditions. An advanced robust gain-scheduling technique, namely linear parameter-varying control, is being investigated by the authors to do this.