Nice try, but...
-It would be great if You try a bit to make curves/arcs more smooth and more resembling their real shape (vertical stabilizer, wing trailing edge etc.);
-also it would really help if You avoid double black lines (I'd say that this line separating main fuselage from tail boom don't really need to be black, just dark;
-the cargo door in the bottom rear fuselage - part of it is outlined in black, part in grey;
-double+ black line where contours of wing, fuselage and engine meet... no, no, no - try to manipulate these contours a bit to avoid it;
-nosewheel - again, replace that black spot in place of wheel axis with proper 3-pixel thick one and perhaps make that metal central part of the wheel wider by 1-2 pixels, so it's contour wouldn't create double black line with fuselage contour;
-shading on the top fuselage vs. shading on cockpit windows - it represents the same width of the fuselage so it should have same/similar number of pixels, although because the fuselage narrows towards the nose, the width of that "light" stripe should gradually narrow towards nose (similarly should happen near the tail boom);
shape of the window frames in the cockpit don't quite represent the actual one.
Ah, and I'd suggest checking the shape of that MG turret on top, specifically it's base.