Very good start indeed. What size is your image? I'd give you this advice, which concerns shading mostly:
-extend the shading on the top of the fuselage, to show its rounded shape
-the shading of the lower fuselage between the engine's shadow and the tailplane needs to be changed. As is now, it's not coherent with the rest of the aircraft's shading
-question of coherence again: the bend on the top of the fuselage is show with shading, but the wingtip bend is done with lighting, which gives the impression it doesn't curve down (looks vertical)
-once again: you've put some white highlight on the fuselage, but not on the engine pod. Adding some highlight to it would give it a nice rounded shape.
-depending on the size of the image, you might want to add stenciling to your aircraft.The A-10 has got loads of it. This is one possible reference:
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Notice how horrible the colours are on that bird.
I know it's always difficult and frustrating to have such things pointed out (as it means more work when you thought you were finished

). Your profile is very nice nonetheless so keep on going. I've learned a lot of things from people's advice here, so it's well worth the frustration.