There is much enlightening info on this topic.
A certain book written about the TWA tragedy referred:
1) to the 'fact' that the FBI (for the first time after an aircraft accident?) rode on the first boats which took law enforcement people to the crash location.
2) that the debris was tightly sealed in a building with unusually high security to prevent access. All accident investigations require some security-but this much?
3) that some sort of missile (propellant?) residue was found on some cabin seats or other debris.
Is any of this true, or none of it true? If some of it is, then why the FBI involvement and such high security, unless a terrorist group secretly claimed to have done it, or a military missile somehow tracked the plane and had the range to hit it? Maybe a missile impact would have produced different damage, but there are so many bizarre facts connected with this case. Even an AF Reserve helicopter pilot with a squadron on Long Island claimed to have seen a missile streak towards the 747. He was interviewed by the media, but he seems to have said nothing after the initial appearance. Is any of the true? I have no idea if there really was some sort of conspiracy (clearly this happens only in the US...let's forget the charges made "over there" or "over here" about Diana's death in the Paris tunnel....), but whether any such proof could ever be released to the media, is very unlikely.
About nitrogen inerting in fuel tanks, there was one known such fatal accident among tens of thousands of flights aboard US-built aircraft per year. How would the FAA's almost secret, safety "cost/benefit" analysis see such a modest loss of life as justification for the huge expense, unless it is a huge attempt (by more than the FAA alone) to keep public/media attention from focusing on any OTHER cause? To divert public attention c o u l d be the main priority here. To hit two birds with one stone, attention can be diverted while time goes by and the public forgets about nitrogen inerting thingies, which might cost airlines nothing. It might only cost the US airlines money.
Anyway, with politics and foreign relations always the highest priority, which even help determine which foreign airlines are deemed safe enough to fly into the US (create the correct paperwork and don't seriously insult the State Department in certain contexts), the administrators might not want to push any bankrupt airline over the edge; these top administrators are all political appointees, as are the heads of the DOT, FBI and Justice Departments etc. The FAA once had a former Thunderbird pilot as the man "in-charge" (
), to put it very loosely.