"Bob Gardner" wrote in message news:JXDIb.16018

....With regard to the fog, however,
there has to be moisture from somewhere...simple expansion is not the
whole
story.

There is some moisture in the pressurization air pumped into the cabin, but
not much. More is absorbed from the bodies on board and evaporating water
and other fluids. Enough to condense when you rapidly drop the pressure
from around 800 to 300 mb.

JG