Swiss I think you’ve got it.
The French will definitely be making the calls on all aspects of the investigation, and subsequent who’s to blame.
Air accidents can be investigated by the home state of the airline, the state the accident occurred in, the state of departure, state of the nationality any passenger on-board and the home state of the aircraft manufacturer. In this case as it was international waters it could be called by either Brazil (state of departure and passengers) or France (state of airline, manufacture, and passengers).
For instance an Air New Zealand 777 crashes in London – The UK Air Accident Investigation Branch (state of accident), the New Zealand Transport Accident Investigation Commission (state of airline) and US National Transport Safety Board (state of manufacture) would all be entitled to investigate, assist and have access to the evidence. Having departed from Hong Kong the Accident Investigation Division of the Civil Aviation Department are also entitled to investigate. This hypothetical accident would be very unlikely to be tampered or fudged with as there are four bodies searching for the cause. Of course it is unlikely that the four nations would send their teams to perform the investigation, they are likely to have an ‘entente cordiale’ to trust each other. The only exception is the NTSB, they always like to get involved seeing as its always America’s fault – either through poor training or manufacture.
Its just easier that the French do it all seeing as they are also the home nation of the airline and manufacturer. Though it could lead to some questionable results; just as in 1988 at Habsheim with AF296 there may be fudging and the pilots put to blame. The evidence was tampered with, the local governor took the black boxes and took about 10 days to hand them to the BEA. It was discovered that the voice recording had been interfered with and jumped and missed at key points!
I made a report on AF296 about the questionable outcome of the investigation – pilot error. This outcome means Air France, nor Airbus are directly to blame – either through poor training, maintenance or design; hence protecting the national interests! For 296 the Captain spoke out against the party line and blamed the brand new aircraft. He lost his job and was discredited on medical grounds. His First Officer kept quiet and kept his job.
I love Airbus but I would rather the truth, than some protectionism by the French authorities.