James,
there are only a couple reasons that urethane clear goes satan, the first is not enough dry time between coats, trapping solvents.
couple questions, is the entire surface of the airframe satin, or just certain parts?
if just parts are, which parts, the upper surfaces?
Did you maintain any airflow through the room you sprayed in after you were done, one thing that can happen with urethanes when you dont maintain airflow, the microscopic reducer and clear molecules that float around in the air will settle back on the surface causeing a stippled, or satin looking finish.
another thing, what solvent did you use? I would have used the absolute slowest solvent available, hmm ok wait, you were using a non reduceing clear. Ok that being said, what catalyst, generally there are several catalysts available to compensate for different temperatures.
If it was glossy when you finished shooting it, and the surface was smooth with no real orange peal, then I would say that you probably were ok on air pressure. UNLESS you totally flooded the surface with clear, but then you would typically have some runs somewhere on the plane..