Estimation of aerodynamic models for the control of damaged aircraft using an innovative differential vortex lattice method tightly coupled with an extended Kalman filter is proposed. The approach exploits prior knowledge about the undamaged aircraft to reduce the order of the estimation problem. Test maneuvers will be designed to improve the observability of the system dynamics. The derived performance model will then be used to determine the aircraft flight envelope, performance parameters and the maneuver limits. The objective is to develop an aircraft performance model online to permit the derivation of viable landing guidance laws for damaged aircraft. Phase I research will demonstrate the feasibility of the proposed concept using a NASA-supplied aircraft simulation. Complete aircraft performance estimation system will be developed during the Phase II research and evaluated in real-time, high-fidelity simulations.