Multipoint electric field measurements on the French C-160 research airplane presented additional verification for a physical model of aircraft-triggered lightning as a bidirectional leader initiated on the aircraft. For the few lightning strikes to aircraft that were not aircraft-triggered, the multipoint electric field measurements proved that these strikes resulted from interception of the aircraft by natural lightning flashes. Video images of lightning channels at 200 frames per second provided the first and only physical evidence of the presence of a positive leader exiting from the positive pole of the airplane's electrical dipole. The existence of a small (<1 A) positive leader current had been predicted in the physical model but had not yet been measured. Weak pulse processes found in magnetic field variations during positive leader development confirm the presence of small amplitude streamers in addition to a continuous leader process. ¿ American Geophysical Union 1992