We examine the path-following guidance of a UAV in three-dimensions and in the presence of quasi-constant but unknown wind disturbances. The analysis and control design are based only on a kinematic model. A first contribution is an alternative description of the dynamics that simplifies the design. A second contribution is the derivation of a guidance law that ensures the global asymptotic convergence to the desired path in spite of wind perturbations. To achieve our objective a simple estimator based on the Immersion and Invariance (I&I) approach is used for the estimation of the wind velocities and tools from robustness analysis for the stability proof.