The ER-2 Lightning Instrument Package (LIP) allows the vector components of the electric field (i.e, Ex,Ey, Ez )to be readily obtained, and thus, greatly improves our knowledge of the electrical structure of storms overflown. The field mills measure the components of the electric field over a wide dynamic range extending from fair weather electric fields, (i.e., a few to tens of V/m) to larger thunderstorm fields (I.e., tens of kV/m). Total lightning (i.e., cloud-to-ground, intracloud) is identified from the abrupt electric field changes in the data. The conductivity probe measures the air conductivity at the aircraft flight altitude. Storm electric currents can be derived using the electric field and air conductivity measurements.