Abstract: In this paper, an engineering approach for determining initial fatigue quality（IFQ） of aeronautic structure details （fastener holes） is introduced. The equivalent effects of a physic -al initial flaw on one or multiple structure details are characterized by equivalent initial flaw size （E1FS） distribution.The growth law of this distribution is described by servie crack growth master curve （SCGMC）. The damage extent of the detail fatigue cracking is determined by crack exceedance probability.In general, the engineering approach is applied to other structure details such as cutouts, fillets, lugs, etc.A number of tests were conducted and a calculation program for optimizing the parameters were written. By comparing the test results with the calculation results, it is demonstrated that the approsch is suitable for durability analysis of aeronautic structures.