According to one implementation, an aviation system 100 includes electric field sensors 112 and a ground system 114 including a computer configured to communicate with each of the electric field sensors 112. The computer is configured to: acquire electric field intensities from the electric field sensors 112 respectively, and generate a first electric field distribution on a ground surface 16 based on the electric field intensities; derive a matrix; derive a pseudo inverse matrix of the matrix; derive an electric charge distribution on the horizontal plane by multiplying the pseudo inverse matrix by the first electric field distribution on the ground surface 16; and derive a second electric field distribution on a flight path based on the electric charge distribution. The first electric field distribution on the ground surface 16 is derived by multiplying the matrix by electric charges temporarily set on a horizontal plane at a predetermined altitude.