I would suggest that whoever it might be, they must be separate from, and independent of, the DOD/MOD and the Airworthiness Authority, which must be separate and independent also.
With respect, Chugalug, you are talking a bit out of your backside.
For example, in the USN & USMC, there are a minimum of two accident investigations for any mishap: a safety investigation, usually led by an O-5 or higher from squadron other than the one who had the crash and with safety privilege as a method that American courts have supported over and over ... and a JAG manual (criminal) investigation, which does not offer privilege that the safety investigation does.
I've been involved in both.
When findings are presented, they are subject to minute scrutiny and endorsement (and not infrequently, inquiries for more info/clarification) from within and without the operational chain of command.
Your accusation that this investigation method, which has been going on for about fifty years, is insufficient or not impartial is loaded with crap.
I'll add to my dismay at your post that it is insulting to a hell of a lot of officers and ranks who get assigned to those investigations (which are exhaustive and exhausting) and the Safety Center who provides a hell of a lot of technical support.
The USAF has a similar set up but I won't comment further on them, as I wasn't USAF.
On top of that, in the Navy, if pilot error is suspected or shown to be a causal factor, another investigation (Field Naval Aviator Evaluatoin Board) is convened to make recommendations to the convening flag officer regarding whether or not the pilot/pilots/aircrew ought to fly anymore, or not. (Providing they are still alive).
Now, is there a problem with manufacturers having to get their teeth pulled in some cases to get critical performance or spec info during such an investigation? Yes, sometimes.
Are there problems with the endorsing chain disagreeing with one another on the import of the findings? I have seen it.
Is that your concern, or are you on the "the military is involved in a cover up" bandwagon ?
