Updated: Nov 29, 2022
Pilots are taught to avoid thunderstorms by 20 miles or more, especially when the thunderstorm is exhibiting severe characteristics such as heavy or extreme rain, hail, high winds or tornadoes. One of the other inherent dangers of a thunderstorm is being struck by a bolt of lightning while in flight. Certainly the threat of a lightning strike increases the closer you are to the thunderstorm. So keeping your distance makes good sense. But what about aircraft-induced lightning?
There are two kinds of lightning encounters. The first one can simply be described as being in the wrong place at the wrong time. Literally the flight path of your aircraft intercepts a lightning bolt that is already in progress. While this is rare, it normally occurs down low when climbing out after takeoff as was the case of this aircraft (shown on the right) on takeoff from the Komatsu Air Force Base off the coast in the Sea of Japan.
The other more likely encounter is one induced by your aircraft. There are many observed cases of lightning strikes to aircraft inside or near clouds that had not previously produced natural lightning. Studies show that about 90-percent of the lightning strikes to aircraft are thought to be initiated by the presence of the aircraft itself. The scary statistic, however, is that 40-percent of all discharges involving airborne aircraft occurred in areas where no thunderstorms were reported. The two separate lightning strikes to Apollo 12 shortly after launch were thought to be initiated by the Saturn V rocket in a region of high instability. Other than these two lightning strikes to the rocket, there were no other lightning strikes in the region six hours prior or six hours after the launch.
While aircraft-induced lightning is still being actively researched, there are a few important characteristics to consider. From the information above, we know that it doesn't take a thunderstorm to initiate a lightning strike. The presence of the aircraft in an environment conducive to an electrical discharge is all that is necessary.