The Multiple Simultaneous Specification controller design method is an elegant means of designing a single controller to satisfy multiple convex closed loop performance specifications. In this thesis, the method is used to design pitch and roll attitude controllers for a Zagi flying-wing unmanned aerial vehicle from Procerus Technologies. A linear model of the aircraft is developed, in which the lateral and longitudinal motions of the aircraft are decoupled. The controllers are designed for this decoupled state space model. Linear simulations are performed in Simulink, and all performance specifications are satisfied by the closed loop system. Nonlinear, hardware-in-the-loop simulations are carried out using the aircraft, on-board computer, and ground station software. Flight tests are also executed to test the performance of the designed controllers. The closed loop aircraft behaviour is generally as expected, however the desired performance specifications are not strictly met in the nonlinear simulations or in the flight tests.