This paper focuses on autonomous path-following flight taking uncertainty and external disturbances into account. Integrated guidance and autopilot are developed using a second-order sliding mode approach that is one of the well-known approaches for mitigating so-called 'chattering phenomena'. The input magnitude for such a higher-order sliding mode approach tends to be extremely large in the initial reaching phase. In this paper, a novel sliding surface is developed using Ackermann and Utkin's

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... method for reaching the surface smoothly to attenuate such extremely large initial inputs along with uncertainty and disturbance compensation. The potential of the proposed methodology is demonstrated with some path-following application under wind turbulence. Performance comparison with a conventional higher-order sliding mode approach is also presented.