Steakman, the biggest problem I remember was penetrating the monsoon over the Bay of Bengal over the Nicobar Islands. A giant line of monstrous storms across track. We had everybody strapped in for ages while we picked a way through, but even then we actually were at one stage 150 miles off track looking weaving a way through.
Strangley enough I was at a lecture a few years back given by a meteorologist/scientist who implied thunderstorms didn't really get any higher than about 33,000'. I pointed out to him that I had been at that altitude looking up at some that seemed to go up above that altitude as if we were on the ground- a good 15 or 20,000' at least. He didn't believe me. It is not unusual for even 747s to be tipped on their sides, with people thrown airborne and damaging the ceiling with head holes, then damaging themselves when they come down again. Aeroplanes are tough. But somehow, if you do get caught like that, all everybody wants to do is sue sue sue- the pilots, the airline...anything that moves. We are invading an alien territory up there- we all have to accept the risks that come with it!