But why doesn’t the gigantic amount of current, which is in the neighborhood of 20,000 amps for a typical lightning bolt, harm the passengers inside the aircraft? Because the hull of the plane forms a Faraday cage! A Faraday cage is a hollow shell made of conducting material. A strong electric field outside the cage will force the charge in the material of the cage to redistribute itself, but the interior space inside the cage remains uncharged. As long as you’re inside the airplane, not on its surface, it can get struck by lightning all day and you’ll be fine — physically, at least, although you may feel a bit freaked out.

Go science!!! Via Geekologie, who got it from Uberreview who got it from Popsci.