This paper proposes a statistical approach able to assess the fastening resistances uncertainties in aircraft assemblies. This method relies on the use of the maximum likelihood estimation method, several statistical tests and/or statistical criteria. Using the Dassault-Aviation measurement database, distribution laws are established in order to characterize uncertainties in the lightning impact on the fasteners. A simple FDTD fastener model is proposed with a wire and a resistance. This generic model can represent any fasteners. The statistical model established from the fastener resistances state after a lightning shot is used to define the stochastic distribution values in the fastener electric model. This model is added to a 3D FDTD parallelepiped generic fuel tank model. In this article, we compare the current distributions between a composite and metallic fuel tank. The results highlight not only the model uncertainties effects on the statistical approach but also the fuel tank material choice impact. Index Terms-Statistical method, finite-difference timedomain (FDTD) modelling, fastener modeling, lightning effects, fuel tank aircraft, composite material.