"Capt.Doug"
There was no visible moisture. The sky was crystal clear. The only wing
contamination possible would have been light frost on the bottom of the
wing
where the fuel had cold-soaked after landing- if the plane had made a
quick-turn. No other aircraft had requested de-icing. I doubt that the
cause
was wing ice.

Frost on top of the wings, and more importantly - on top of the T-tail is
highly likely. I have flown a T tail jet for 25 years and you can get frost
on top of the wings and tail very easily in the early morning with the right
conditions.