I haven't seen ball lightning but I once flew with a man who had. He said they were near thunderstorms, the was a certain amount of St Elmo's fire on the windscreen, when suddenly they saw coming towards them from right in front a ball of light. It came through the flight deck windows and then bounced sedately between the two pilots and right on down the aisle where it disappeared, presumably, out through the rear pressure bulkhead. The four men on the flight deck all saw it, as did most of the passengers and cabin crew. I have no reason to disbelieve him, he was not given to flights of fancy.
My question is; how is it possible for such a phenomenon (one would assume of an electrical nature) to penetrate a Faraday cage?
The only strange phenomenon of this kind that I have witnessed was when near thunderstorms, paralleling the ITCZ between Colombo and Kuala Lumpur. There was lightning in the vicinity and a certain amount of St Elmo's fire on the windscreen which was followed by an enormous purple cone that seemed to spread out to infinity in front of us. After a while it disappeared as suddenly as it had appeared. We weren't struck by lighnting but were much amused by the colour of the cone. We had the Anglican Bishop of Singapore on the jump seat at the time (he had asked to see the flight deck) and its colour exactly matched the colour of his shirt below his dog-collar.