Abstract: A method of statistical analysis for assessing reliability of main wing components used pairwise in aircraft is presented.The statistical variability in structural fatigue life（time of crack formation）,the probability distribution of size of the crack missed in inspection and the statistical distribution of applied service loads are considered and the effects of crack propagation rate and the fracture toughness of materials are taken into account.The paired wing components may be considered as a cascade system.After obtaining the distribution of their minimum fatigue life,the probability distribution of initial crack sizes at the beginning of any inspection period can be derived from crack detection probability curve and crack propagation equation.On the other hand,the residual strength of a cracked component can be given as the function of the time after crack initiation in consideration of the appropriate crack growth model and the fracture toughness of material together with applied service load.Finally,two formulae for estimating failure probability in any inspection interval are derived respectively.One of them can be adapted to the case that a component failure results from the crack occurred in that interval,another to the case that the failure is caused by the crack being prior to the beginning of the interval.A numerical example for the failure probability of main wing spars of a fighter is given.