it was either the Navy, or an accident. Not really another option.
Or someone didn't want someone or something leaving the country on that plane and shot it down intentionally. The GAO admitted to losing accountability on exported Stinger missiles.
The FWD cargo door opened in flight. Look up UA 811. The exact same spot except it made it back to earth in one piece. If you look at 800 wreckage photos you will see the paint transference above the windows.
It was the Navy, I am sure. I believe at the time only the Russians, Brits, and US Navy had that capability!
USN is a possible theory but the thing that troubles me about that is that how would it ever be kept secret after so long and so many people aware of the truth ?