A multiple Station analysis and an exponential time trend are presented for estimating the weight of the structural box of an aircraft wing. Optimum weight s calculated from the multiple station analysis which is based upon a simple beam representation of a semi-wing. It was found that a high correlation exists between the ratios of optimum weight to actual weight and time. The ratios are estimated by a time function, 1-exp-(a+bT), where T is time of first flight in months from January 1944. Errors of estimation are found to be small and the root-mean-square error is less than nine per cent. All aircraft are placed in a single category. The estimating equation for structural box weight is W(B+S)e = kW(B+S)o where k is the function of time.