IMMP, the Interactive Maneuvering Model Program is a simulation of the displacement of the center of gravity for a fuel mass in a semi-depleted fuel tank during aircraft maneuvering. It operates on the basic input data of weight of remaining fuel, vehicle roll angle, and vehicle pitch angle. The simulation is accomplished by way of a finite element analysis on the cross sectional area of the fuel tank to evaluate iterative later and vertical c.g. drift, followed by a complete c.g. determination based on coordinated ""stacking"" of cross sectional mass properties elements. Cross sectional area of the subject fuel tank are defined by a two dimensional array within the software. Array elements occupied by fuel in a full tank are active, while elements occupied by air, structure, or obstructions are inactive. This allows changing the cross sections within the tank by changing the ""active"" elements of the cross sectional matrix. IMMP provides accurate and cost effective mass properties input to aerodynamic flight simulations for the purpose of operational and technical evaluations of aircraft performance.