Abstract: The present invention is embodied in an apparatus and method for generating fatigue spectra on a chosen aircraft for which a Finite element model is available and for which a library of external load summations at key interfaces and key fundamental parameters are available from an aeroelastic analysis. The fatigue spectra generation system of the present invention represents a profile of stresses endured by the aircraft due to numerous events, such as ground and maneuver events, occurring during the life of the aircraft. The system calculates a total stress based on load and unit conditions associated with outside events by factoring up the unit conditions to derive individual stresses for each event and by summing all unit conditions.