Planes are designed to withstand and fly safely when struck by lightning.
More lightning strikes occur while in clouds, during the climb and descent phases of flight, than any other flight phase.
The reason is that lightning activity is more prevalent between 5000 to 15,000 feet (1524m to 4572m).
Airplanes that fly short routes, in areas with high incidence of lightning activity, are likely to be struck more often than long-haul airplanes operating in more benign lightning environments.
A Boeing paper on lightning strike says a single bolt of lightning can contain as much as 1 million volts or 30,000 amps.
The amount and type of damage an airplane experiences when struck by lightning can vary greatly, depending on factors such as the energy level of the strike, the attachment and exit locations, and the duration of the strike.
The aluminium used on most commercial aircraft conducts electricity and allows the lightning to pass across the skin of the aircraft, with the current usually exiting the aircraft at the tail.
Composite aircraft such as Boeing Dreamliners have conductive mesh woven into their fuselage to help them conduct electricity.
Static wicks (small wires that are screwed into the trailing edge of plane wings) discharge static electricity that an aircraft picks up as it moves through the air but also dissipate a lightning strike.
During the initial stages of a lightning strike on an airplane, a glow may be seen on the nose or wing tips caused by ionisation of the air surrounding the leading edges or sharp points on the airplane's structure.
The Boeing paper says passengers and crew may see a flash and hear a loud noise when lightning strikes the airplane.
''Significant events are rare because of the lightning protection engineered into the airplane and its sensitive electronic components.''
The aircraft fuel tanks have skin around them which is thick enough to avoid a burn-through.
Boeing says that electrical systems in a plane are designed to be resistant to lightning strikes, but a strike of unusually high intensity can damage components such as electrically controlled fuel valves, generators, power feeders, and electrical distribution systems.
Most of the external parts of legacy airplanes are metal structure with sufficient thickness to be resistant to a lightning strike. This metal assembly is their basic protection. The thickness of the metal surface is sufficient to protect the airplane's internal spaces from a lightning strike.
When an airplane is struck by lightning and the strike is evident to the pilot, the pilot must determine whether the flight will continue to its destination or be diverted to an alternate airport for inspection and possible repair.
Direct effects of a lightning strike can be identified by damage to the plane's structure, such as melt through, resistive heating, pitting to structure, burn indications around fasteners, and even missing structure at the airplane's extremities, such as the vertical stabiliser, wing tips, and horizontal stabiliser edges.
The United States National Lightning Safety Institute lists seven commercial aircraft losses between 1959 and 1988 due to lightning strikes with the crashes of a Pan Am Boeing 707 in 1963 and a LANSA Lockheed Electra in 1971 both claiming 81 lives.