NVN:-
Who would take responsibility for a military aviation incident? In the US NTSB is not involved in military accidents.
The UK AAIB (Air Accident Investigation Board) is not responsible for investigating UK Military Air Accidents, but may be involved if invited. The MAAIB is the responsible body which, together with its stable-mate the MAA, is part of the MOD. Thus a similar set up exists in the UK and the USA, whereby Military Airworthiness Regulation and Air Accident Investigation are subsidiary functions of the owner/operators, ie the DOD/MOD and their dependent Services. That is why UK Military Airworthiness and Air Accident Investigation are both in a state of crisis.
You ask who would take responsibility for investigating Military Air Accidents. 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. Easy to say and very difficult to do, I admit, but the last 30 years has shown that the clash of interests that the present incestuous system allows for has cost much blood and treasure.
In short, in the UK the MAA and MAAIB must become separate and independent of the MOD and of each other. Only then can we expect Airworthiness Provision and Air Accident Investigation that can be relied upon. I would respectfully suggest that a similar course might benefit US Military Aviation Safety also.