Traditionally, airborne store design has been based on service life criteria similar to those used for aircraft development. Recent research has shown that an airborne store may be exposed to a unique loading environment and may therefore require a different approach. Moreover, flight loads data for aircraft and airborne stores are normally difficult and expensive to obtain, because resources are not available to fly a sufficient variety of combinations of aircraft, stores, and mission types. Finally, the increased life of many stores has made fatigue life an important consideration in design. These considerations led to development of an approach to building flight-load spectra for fatigue testing of externally mounted airborne stores (that is, fuel tanks, missiles, bombs, etc.) using time-history load data collected from U.S. Air Force and Navy training flights. The data are processed using a “racetrack” type data compaction algorithm to yield sequential peak/valley pair files, and then reorganized to build new mission profiles. Finally, the new mission profiles are weighted by expected frequency of occurrence and organized to reflect the expected service use over a period of time.