"Robert Lyons"
The effect Peter is describing (if I understand correctly) should be very
common, basically visible whenever you are flying over the deck. It's the
light of the sun, back-scattering off the clouds. The ground needn't be at
all
visible (better if it's not, in fact) and the 'glow' will be diffuse and
un-
focused.

Actually I see it on the ground but it is diffuse and unfocused - like a
very strong headlight shining on a very distant area. You just get a
diffuse bright spot.

I think I get Peter's concept and understand it but can't quite get it to
'intuit'. But makes some sense. Can't quite understand why the area on the
ground where sunlight would reflect back at 180deg (or normal to the average
surface) would be so much brighter than points where the sunlight would
reflect back at say 45 deg to the avg surface. Doesn't make sense when I
think of a forest of trees, but it is quite clear when same light refects of
a truck on a highway. So I kind of get it. Thanks Peter and Robert.