In order to retrieve the lightning attachment points, 12 sensors distributed over the aircraft continuously monitor the local electric and magnetic field. The selection of the number and positions of the sensors is described in [4]. The ILDAS is triggered by sudden changes in the field strength in the aircraft. The sensors then determine the local magnetic fields, retaining pre-and post-trigger data over the time span of about 1 s. After landing, the data are compared with possible field distributions derived for a number of current path scenarios [3], and the most likely entry and exit regions are determined.