The findings of this paper show how the three velocity vectors and the spatial position of a disintegrated aircraft at the time of initial disintegration may be established from ground wreckage. Essentially, the method consists of finding, (1) an error function by using ground wreckage locations and characteristics; and, (2) the minimization of the error function. The parameters of initial velocity and height associated with the minimum error provide an estimate of the conditions existing prior to aircraft break up. The proposed method completely eliminates trajectory plotting and is entirely automatic where error calculation and minimization are concerned. A •trial-and-error' method is used to determine the best initial estimate for the minimization procedure. The minimization technique proceeds from this estimate and converges to the minimum error and its associated initial conditions. Minimization problems introduced by wreckage scatter are overcome by reducing the number of variables and/or by using several other possible initial estimates. The procedures for calculating the aircraft disintegration sequence based on known initial break-up conditions and the locating of objects which have separated from the aircraft are also described.  The methods depicted here have been programmed for a digital computer and have been tested using real examples. The results of the programs are in fair agreement with the findings established by previous authors, who used manual and/or observational methods.