Steve,
I will attempt to help you, but to do this I need a bit more info
what kind of spray gun,
pressure at the gun, (or pressure at the compressor, and how long the hose is and what size is the hose)
brand of paint
brand of thinner
temp
humidity
how far away are you holding the gun from the surface
how much thinner
short of having that info, its virtually impossible to really diagnose the problem. sure a lot of guesses can be made but to really address the issue I need that info.
another thing to help diagnose this, you may want to test the adhesion of the paint you sprayed. one method (a bit aggressive) is to use good masking tape and stick it down over a part of the plane you know the covering is well stuck, then pull the tape up, if the grey lifts off the substrate it most likely is going on to dry for One of many reasons. be advised this is NOT a test to be taken lightly, you can pull underlayments up with it. the less potentially harmfull method would be to wetsand an area that you sprayed, pick the roughest looking spot, and wet sand with say 400 . You will need to sand until you start to see the underlayers showing slightly, if the grey feathers well, (no discernable sharp edge where layers seperate) then it is probably stuck andmost likely the problem is with the application as opposed to the material drying to fast.
If you let me know the other info I will help as much as I can before you "attack" your plane