The most important task in tests of resistance of aircraft structures to the terorist threats is to determine the vulnerability of thin-walled structures to the blast wave load. For obvious reasons, full-scale experimental investigations are carried out exceptionally. In such cases, numerical simulations are very important. They make it possible to tune model parameters, yielding proper correlation with experimental data. Basing on preliminary numerical analyses - experiment can be planned properly. The paper presents some results of dynamic simulations of finite element (FE) models of a medium-size aircraft fuselage. Modeling of C4 detonation is also discussed. Characteristics of the materials used in FE calculations were obtained experimentally. The paper describes also the investigation of sensitivity of results of an explicit dynamic study to FE model parameters in a typical fluid-structure interaction (FSI) problem (detonation of a C4 explosive charge). Three cases of extent of the Eulerian mesh (the domain which contains air and a charge) were examined. Studies have shown very strong sensitivity of the results to chosen numerical models of materials, formulations of elements, assumed parameters etc. Studies confirm very strong necessity of the correlation of analysis results with experimental data. Without such a correlation, it is difficult to talk about the validation of results obtained from "explicit" codes.