The aircraft flight control problem is addressed via a nonlinear adaptive backstepping control. A reconfigurable flight controller is designed that achieves robust, high accuracy command angle tracking in spite of uncertain aerodynamic coefficients. The backstepping controller makes use of a recursive procedure that breaks down the control problem for the full system into a sequence of designs for lower order systems. The angular rates of the aircraft are considered as virtual inputs for slow dynamics, which includes velocity roll angle, angle of attack and sideslip angle, to track the given commands. It is assumed that the aerodynamic coefficients include uncertainties, and a gradient projection algorithm is used in an adaptive controller to estimate the uncertain aerodynamic coefficients. Stability of the proposed adaptive backstepping controller is shown and discussed. Finally, these results are applied to a nonlinear six-degree-of-freedom aircraft model. Simulation results are presented to demonstrate that the stability and high accuracy tracking performance is accomplishedin spite of uncertainties in the model.