On average, all airliners are struck several times by lightning every year. What are the risks ? Should we be afraid of this kind of incident?
In November 2017, a KLM plane on the Amsterdam–Lima line was struck by lightning just after taking off from the Netherlands (see video below). This did not prevent it from continuing its journey to Peru. In October 2011, this was also the case for a dozen planes of the Finnish airline Finnair. A couple of the planes had to make a u-turn but the remaining flights were apparently able complete their journey safely.
So what are the risks? Before an airliner is allowed to fly, it must be certified “lightning resistant”. On the other hand, these same planes are struck by lightning on average every 1500 hours of flight, and although the pilots do their utmost to dodge the stormy episodes, they are sometimes inevitable.
Any device that has no choice but to fly through an atmosphere heavily charged with ions is likely to trigger a flash. Indeed, a stormy cloud generates an electrostatic field covering several kilometers, and when an aircraft crosses this perimeter within 20 kilometers of distance, the pointed ends of the aircraft help to amplify the field and have a high probability of triggering a lightning.
Fortunately, the cabin of the plane acts like a Faraday cage, thus protecting the passengers. On the other hand, the lightning can cause minor damage such as the destruction of sensors. Also, the electronic system of the device may be affected by the electromagnetic field from the storm.
Predispositions are made by airliners to avoid any serious failure, starting with the protection of the most sensitive point of the aircraft: the kerosene reserve. Indeed, a simple spark could ignite the fuel!