Quantitative Feedback Theory (QFT) is a control systems design methodology which can be applied to the design of both scalar and multivariable control systems. This frequency domain technique designs controllers which achieve a set of performance and stability requirements over a specified range of plant uncertainty. The QFT design technique is particularly applicable to flight control systems (FCS) design since modern combat aircraft have a high degree of inherent airframe instability and a large variation in plant parameters over a range of flight conditions. QFT controllers also have decoupling properties for multivariable systems as is demonstrated in a design for an Advanced Short Take-Off and Vertical Landing Aircraft at a single operating condition. The control system design will be performed with the aid of QFT design software running on a Mathematica platform.