This paper was presented at the Nineteenth National Conference of the Society of Aeronautical Weight Engineers at Los Angeles, California, May 16 – 19, 1960. The “Unity Equation” method presented in this paper is designed to present airplane weight estimates in terms of available fuel to weight ratio, gross weight, wing loading and other important variables. The method is flexible and accurate, and is compatible with performance evaluation parameters. Optimum values of related weight-performance parameters are obtained through the application of this method. This procedure inherently defines airplane weight growth and consequently, does not require the separate definition of growth factor found in other approaches. Several equations for estimating the weight of functional weight empty groups are presented and are substantiated by correlation plots. This method can be applied to a wide range of aircraft types including VTOL, STOL and conventional airplane configurations.