1. A method of associating deferral procedures to a fault model for complex systems based on historical data, the method including the steps of: analyzing the historical data for deferral information to identify a plurality of deferral procedures; associating each of said plurality of deferral procedures with a corresponding one or more of a plurality of standard repairs; linking each of said plurality of standard repairs with a fault code; and associating each of said plurality of deferral procedures with one or more of said fault codes that were linked, respectively, with said one or more of said plurality of standard repairs to thereby provide a set of associations between said plurality of deferral procedures and a plurality of fault codes.