Airborne Wind Energy (AWE) refers to systems capable of harvesting energy from wind by flying crosswind patterns with a tethered aircraft. Accurate models are crucial for tuning and validation of flight controllers. Due to the non-conventional structure of the airborne component, an intensive flight test campaign must be set where maneuvers are performed for parameter estimation purposes. In this paper, we optimize maneuvers for the longitudinal dynamics of a rigid wing AWE pumping system by solving a model-based experimental design problem that aims to obtain more accurate parameter estimates and reduce the flight test time. We consider a trim reference condition of the aircraft and constraints are enforced in order to prevent flight envelope violation. Finally, the optimal solution is implemented in the Flight Control Computer (FCC) of the prototype developed by Ampyx Power B.V. and validated under realistic flight conditions.