Commercial passenger aircraft are on average struck by lightning once a year. The effects of lightning on aircraft and helicopters are minimal for low-amplitude strikes, but higher-amplitude strikes may result in expensive delays and important repair and maintenance.

The present certification threat level is derived from cloud-to-ground lightning strike data measured on instrumented towers. While historically this threat definition has served the purpose of lightning protection adequately on metallic airframes, modern aircraft incorporate an increasing amount of composite materials that make them more susceptible to damage. Moreover, aircraft now employ more high-authority electronic control systems that are susceptible to upset and damage. As a result of the introduction of extra protection measures the advantages of modern materials could be cancelled by the addition of weight and higher cost.

To be able to design appropriate lightning protection, fixed-wing aircraft and helicopter manufacturers have a strong need for a good definition of the threat that lightning poses to aircraft.