Nicely done. I like the way you did the metal shading
. It seems now to look a little arcadey. I would add some weathering and dirt to it.
What I do is make a new layer on top of everything else. Then, take a 1 pixel brush in black and run it down the fuselage/wings the way wind blows over it. Then, if you use Serif (Which I think you do), blur it to the max it can. Not Guassian, but just regular blur, and see how it turns out.
