I'm with ink, it's a good first skin but it could use a little work. Mine does so don't let it get you down, it's a learning process.
If you were smart (don't be stupid like me
) you will have the panel lines, rivets, color, art, weathering, bump map and specular map in a separate layer. This makes it easy to tweak large areas without affecting others. I am dumb because I allowed the panel lines and the rivets to be in the same layer (same for the panel highlights and rivet shadows, they share their own layer as well).
Speaking of rivets, I'm noticing a distinct lack of them. Did you not add any to the skin? While it is a tedious task trying to make sure all of the rivets are accounted for, it helps add a nice layer of depth to the skin when it is done right.
Make all the panel lines in the layer a grey scale color of about 40-45 and play around with some blending methods.
Once you have the panel lines issue fixed, then you can add some chipped paint to the texture. I usually prefer to start at the joint of 3 panels or more for chipping pain, since this is where it is most likely to start. You can modify the base layer (the olive drab layer with the logos) but I would not recommend this, instead make a separate layer and use the starting grey scale color (grey scale 50, 60 or whatever you chose to use). Mark the outline of the panel lines, just a bit, then use your smudge tool to smear it to alpha channel 0.
By the way, I haven't tried that technique yet but I have plans to do it for my skin while I'm updating.
Some more wear you can add is on the tops of the wings next to the cockpit to give the effect of heavy wear. Ink also mentioned "sand blasting" and he has a good point. On the bottom of the flaps, right behind the wheel, apply
very heavy paint wear to the base texture. I want to see bare metal baby!
I would also add a touch of sun fading as ink also mentioned, just lighten the base texture a little bit. Take ink's advice with the exhaust as well, it's definitely needed.
All in all, good skin. Keep working to add some more aesthetics and I can see it being a winner.