Something to think about- dark lightening

Dark lightning, or terrestrial gamma-ray flashes that occur in storm clouds tend to occur at the same altitudes as commercial airliners and some of the outburst can reach dangerous levels, new research has found. However little progress has been made on attempts to discover whether these flashes pose a radiation hazard to airline passengers due to a poor understanding of what causes them in the first place. Compute models suggest that flashes are caused by an extreme form of lightning that is not visible, hence the term dark lightening. Current estimates state that at top of thunderstorms, at about 40,000