Originally Posted by
lomapaseo
Lots of other considerations like
country of accident
country with most passengers/citizens involved
issues relating to operation, Weather, ATC, Airport, pilot training etc.
issues relating to airworthiness of aircraft or engines
Availability of pertinent facts or investigating expertise including manpower
The state of occurrence has responsibility for the investigation, as per Annex 13. Other interested parties - the state where the aircraft is registered, the state of manufacture, etc - are entitled to be affiliated to the investigation, in this case PNG and the USA. That doesn't prevent the responsible state from delegating part or all of the investigation (but not the responsibility for it) to any state of its choosing.
We know, for example, that the FDR and CVR have gone to PNG for analysis (overseen by FSM investigators), whereas the EGPWS has gone to the manufacturer in the USA.
Regardless of who is carrying out various parts of the investigation, the protocol is that the lead state (FSM) is responsible for release of any information on its progress. That, so far, has taken the form of 8 press releases at the last count, plus an undertaking to publish the usual interim report within the prescribed 30 days.