Lightning occurs at all levels in a thunder-storm. The majority of lightning discharges never strike the ground but occur between clouds or within the same cloud. However, aircraft flying several miles from a thunderstorm can still be struck by the proverbial "bolt out of the blue." Electrical activity generated by a thunderstorm may continue to exist even after the thunderstorm itself has decayed. This electrical activity may drift downstream and is usually found within the cirrus deck that at one time was connected to the thunderstorm cell.

A charge also may buildup on an aircraft after it has been flying through clouds and precipita-tion, including snow as well as rain, or solid particles such as dust, haze, or ice. The larger the aircraft and the faster it flies, the more particles it impacts, generating a greater charge on the air-craft.

The electrical field of the aircraft may interact with the cloud, and an electrostatic been struck by lightning or have experienced electrostatic discharges on the ground or at altitudes ranging to at least 43,000 feet. Most lightning strikes occur when aircraft are operating in one or more of the following conditions:

It should be noted that all of these conditions do not have to occur for a lightning strike or an electrostatic discharge to take place.

Lightning strikes can cause severe structural damage to aircraft. Damage to aircraft electrical systems, instruments, avionics, and radar is also possible. Transient voltages and currents induced in the aircraft electrical systems, as well as direct lightning strikes, have caused bomb doors to open, activated wing-folding motors, and made the accuracy of electronic flight-control navigational systems questionable.

Pilots and crew are not immune to the effects of lightning strikes either. Flash blindness can last up to 30 seconds, and the shock wave can cause some temporary hearing loss if headphones or some form of hearing-loss-protection gear is not worn. Some aircrews have even experienced a mild electric shock and minor burns.

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