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The imprecision of altimeter system in higher altitudes, utilized by aircrafts in past decades, although adequate for lower levels, imposed that minimum separation between flights levels FL290 (29000 feet) and above had to be 2000 feet. This higher separation limits aircraft capacity on these levels where jets are more efficient and, therefore, is undesirable to airline companies, taking account, principally, the fuel economy. The advance of electronic technology in altimetry system has permitted to obtain a better precision of altitude measurements and, thus, reducing the minimum vertical separation between these levels to 1000 feet became safer, showed by figure 1. This process is called RVSM (reduced vertical separation minimum) and presents some characteristics such as introduction of 6 news flight levels. This process defines special requirements related to airspace and it was implemented in North America and Europe in last years.

Lightning is a high voltage and high current phenomenon and it originates by build up of electrical charge in the air or, more commonly, in clouds. It is constituted of an electric current peak of short duration (0,5 ms) and high intensity (200 kA), followed by a low intensity (400 A) but high duration (1s) periods. The lightning effects in aircraft can be divided in two groups: direct effects (physical effects such as melting, rupture, damage of surfaces and structures due to conduction of lightning current or high power magnetic force) and indirect effects (electromagnetic fields generating levels of transient voltage and current on interconnecting wiring and cable leads within the equipment circuits eventually damaging internal components).