Lightning poses a threat to aircraft in flight. To mitigate this threat, the U.S. Air Force requested a study of lightning distances. Three-Dimensional lightning data were examined for this study, spanning 1 March 1997 to 31 May 2001 and obtained from the Lightning Detection and Ranging System (LDAR) at the Kennedy Space Center, FL. The LDAR data points were first grouped into lightning flashes and branches using spatial and temporal criteria. Rawinsonde data were vertically interpolated to determine the temperature at the flash source point and each branch end point. The horizontal distance from flash sources to branch end was calculated. Percentiles of branch distance were examined as a function of altitude and temperature of the flash source and branch end points. The longest 99th percentile of branch distance (35 to 40 km) was found at 2 to 7 km altitude and between 10 and -20C. The altitude range of the longest branches remained similar by season, but the longest branches were found in the winter and spring months, with summer and autumn distances shorter by 5 to 10 km. Summer results showed longer branch distances to the south and the winter data showed a significant elongation to the north
