Wow. Went right through the plane.
It is actually a bit of a muffled sound, yet loud enough to be somewhat scary when it hits the plane.
We got hit off Barcelona half an hour after departure. I was looking at the dark grey clouds and thought "Oooops, it's going to get us" - when the lightning struck.

As I had intuitively expected it, I was the only passenger laughing out.
But the plane turned around with the captain announcing a "routine inspection". Of course.
After a safe landing, we were immediatly taken to another plane already waiting. Sure. Routine inspection.