A formulation of optimal trajectory planning problem that always results in a flyable solution for the MAV is presented. MAV flights in winds are formulated as nonlinear optimal control problems, with proper constraints on states and controls. MAV motions can be adequately represented by a dynamic point-mass model for the purposes of trajectory optimization. The effect of winds on aircraft flights is highly dependent on the overall speed of the aircraft. To facilitate the studies of optimal air vehicle trajectory planning in winds, it is useful to systematically characterize and classify the significance of wind based on typical airspeeds of aircraft. When airspeeds are larger than wind speeds by several orders of magnitude, it may be expected that the effect of wind is generally very small. In this formulation, one primarily seeks to minimize the difference between the final state of the MAV to the target state, as opposed to specifying the target state as the final state.