Electromagnetic threat could be an issue for aircraft safety. HIRF and lightning are the more known threats. However, even if the scientific community seems to focus on the increasing danger of passengers' electronics devices (PEDs) on board aircraft with respect to interference with aircraft systems, Electrostatic Discharge (ESD) appears to be a more harmful threat for aircraft systems than PEDs. ESD charging and discharging phenomena may lead to interferences with communication and navigation systems. More, ESD also generates E field pulses and voltages transients that could be fatal to some electronic systems components.With composite aircraft, because of the lack of skin conductivity, ESD could become a very high concern for systems immunity.