The accumulation of a net electrical charge on the surface of aircraft, or the separation of charge into two concentrations of opposite sign on distinct portions of the aircraft surface. Net charges appear as a result of autogenous electrification when aircraft fly through clouds of ice crystals or dust. Charge separation occurs by induction when aircraft fly through regions of strong atmospheric electric field, as in thunderstorms. Charging may also occur by the engine exhaust carrying away a net charge leaving the aircraft charged. Development of large local charges on aircraft parts may lead to appearance of corona discharge or St. Elmo's fire and is almost always accompanied by poor radio communication due to so-called precipitation static.