Years ago when BEA were flying Comets out of Geneva a just departed Heathrow bound Comet was struck by lightning at about 3000 feet. A friend [on duty BEA Hostie] said that the cabin lit up as a huge bang coincided with a grapefruit sized ball of fizzing bright light which appeared in the aisle and drifted towards the rear and it frightened a lot of people until it suddenly slewed into an overhead bin with a bang and a few sparks.