This picture is undeniably cool, but not what most people want to see from their window as they fly during the holiday season. Lightning is scary for the passengers, but it's no big deal for the plane. There hasn't been a plane downed by lightning for forty years. Here's why.
I have seen lightning from a plane window. It turned the clouds around the plane into mountains of bright red and green fire, and despite a trooper of a flight attendant insisting that it was only "lights from other planes," no one was fooled. She probably shouldn't have bothered to lie. Though air collisions are extremely rare, other planes are more dangerous to an airplane than lightning is. On average, every commercial plane is struck by lightning once a year.
The three major dangers with lightning are the chance of a spark near the fuel, the temperature of the lightning itself hurting the structure of the plane, and the chance that the charge could move to the interior of the plane and mess with its instruments. A spark igniting the fuel was what caused the last airline disaster due to lightning in 1967. After that, planes were redesigned to keep such sparks and fuel ignition from happening. The temperature is extreme, getting up to 30,000 degrees centigrade but too brief to leave more than a scorch mark on the plane.
The electrical interference itself is the most fearsome, but is the least likely disaster to happen. Planes form natural Faraday cages. To be fair, Faraday cages are not that hard to make. Benjamin Franklin noticed, when he was first experimenting with electricity, that charge applied to a bucket or cage-like object seemed to distribute itself only on the outside of the object. Michael Faraday studied this more extensively, and started designing cages that we have now. He noticed that if he charged up enclosed metal objects from wire mesh to covered soup tureens, he could leave anything inside - even electrically responsive things like metal balls and wires - and they were unaffected. Objects on the outside of the cage were zapped. The charge ran over the outside of the surface of the Faraday cage, as long as that surface was relatively smooth and unbroken. Planes are made of aluminum, which is an extremely good conductor. Aircraft that aren't made of aluminum often have a thin coating or layer of the conductor in order to let charge flow smoothly over them. They distribute the charge on their outside surfaces, leaving people and equipment undisturbed inside. The lightning then discharges into the air - either heading toward a nearby cloud or the ground. The main danger of lightning now is disorienting the pilots.
Planes do land as soon as possible after being struck by lightning, but that is mainly as precaution. For the most part, in a plane is one of the safest places to be when lightning is around. Still, I'd rather fly through clear skies.
Image: Aindrila Mukhopadhyay