The purpose of this paper is developing an efficient flight control strategy in terms of time response characteristics, robustness with respect to both parametric uncertainties and un-modeled nonlinear terms, number of required measurements, and computational burden. The proposed method is based on combination of a classic controller as principal section of the autopilot and a multi-objective genetic algorithm-based fuzzy output sliding mode control (FOSMC). FOSMC not only modifies robustness of the classic controller against uncertainties and external disturbances, but also modifies its time response for wide range of commands. FOSMC is a single input-single output controller that is based on the system output instead of the system states. In this situation, the proposed autopilot does not require measurement of other variables and observer, and also it is practicable because of considerable reduction in rule inferences then computational burden. As a critical application, the proposed method is applied to design the altitude hold mode autopilot for an UAV which is non-minimum phase, uncertain, and nonlinear.