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A damage tolerance analysis method for aircraft structural integrity, designated as the effective block approach, has been developed and subsequently applied to predict the fatigue crack growth life of aircraft structures subjected to flight spectrum loading. The predictions by the method were made not based on constant-amplitude crack growth data, but instead relied on spectrum crack growth data obtained from previous full-scale fatigue tests or representative coupon fatigue tests. The spectrum crack growth data were normally measured from observations of the fracture surfaces by quantitative fractography. Verification and consistency studies of the method were performed against fatigue test results under different flight spectra. The predicted fatigue lives and inspection intervals for fracture-critical locations in aircraft structures were found to be in close agreement with representative coupon and full-scale fatigue tests. This study has demonstrated that the method provided significant advantages in damage tolerance analysis over conventional fatigue lifing approaches for military aircraft structures and components. It was also found that the work has improved the value of structural integrity advice provided for some Royal Australian Air Force air platforms and supports the safe operation of the fleets through to their planned withdrawal date. [ABSTRACT FROM AUTHOR]