This paper provides a passivity based adaptive trajectory tracking controller for quadrotor dynamics. The proposed controller guarantees global asymptotic tracking for any desired smooth trajectory, and this is achieved, through parameter adaptations, without precisely knowing the mass and moment of inertia of the quadrotor. A convergence criterion for the mass estimate is given. In addition, bounded disturbances on the thrust and torque are considered, and it is shown that the tracking error is globally bounded under mild conditions. Simulations are carried out to illustrate the control performance.