HPM and UWB sources can represent a threat for the sensitive equipment of various military and civil targets. The paper focuses on effects on aircraft and discusses the modeling possibilities available today to estimate such a threat for modern airplanes. An evaluation of voltages at the input of electronics, based on measured attenuations of a HPM field in a cavity and induced voltages in the wiring of a car which can be considered as being similar to the structure of an airplane cabling, is presented. This estimation shows the potential danger for the electronics submitted to a low level HPM