I have played SP for about 2 years now and I think it needs a few more kind of material!

For example:
-Fuselage:

+Windows
+Doors
+Interiors (if needed)
+Glass fuselage
+Wiring system through the thing
-Wings:
+Many more types of wings(for fighter jets, commercial jets,etc...)
+Flaps, slats
+Winglets
And if you can, add a simulator to see if the aerodynamics work before flying it or posting!

Thank you!