I was flying from HKG to YVR in November and over Japan the plane (330?) dropped over 100 ft. My brother in law screamed (that could be a whole new thread.) My sister in law asked the pilot at the end of the flight what had happened. He said we had flown over an erupting volcano. I cannot see the pilot making this up, but isn't that a very unlikely occurence? It seems like flying over a needle in a haystack. Oops - mixed metaphor.