Risk of lightning striking
Electronic counters produce data which provide an estimate of about about two lightning strikes per sq km in temperate zones and between 10 and 15 strikes per sq km in tropical zones each year. Lightning discharges between clouds occur about twice as frequently. In forest areas in the USA it has been estimated that one sizeable fire results per annum from lightning for each 40 sq km of forest. Estimates for lightning-caused deaths are: USA, 160 per annum; West Germany, 41 per annum (92 people struck each year). Despite assumptions to the contrary, lightning may cause fatal damage to aircraft. It has been estimated that over Europe one aircraft is hit by lightning for every 2400 flying hours, and once every 6,000 flying hours over oceans. The cost of damage to electrical and electronic devices due to secondary effects of lightning may be ten times higher than that produced directly by a stroke of lightning.