Actually, it is the FBI's job to investigate such an incident, if it is thought that a crime may be involved. Since airplanes just blowing up is pretty rare (there have been about 15 instances of fuel explosions from all causes in all the years of jet flight) and airplanes blowing up because somebody blew them up is unfortunately more common, the FBI took the lead at first. There was a lot of tension as the NTSB guys, who are experienced in wreckage examination, began to see that there was no evidence of a bomb or missile. FBI guys, looking at the wreck, had the same reaction a lot of people do: "It must have been a bomb. Nothing else could be so devastating." But the jurisdictional issue was ultimately sorted out. In earlier cases the NTSB has sometimes handed off to FBI when an accident turned out to be less accidental, and sometimes they've worked together.
Even in the Hindenberg accident, the FBI initially responded and continued to sit in on the investigation, in case sabotage turned out to be the cause (that was as controversial in its day as 800, 59 years and two months later). The FBI never thought it was sabotage, but they put agents on the case to liaise with the Commerce Department's aviation experts. The forerunner of today's NTSB determined that the accident was caused by a hydrogen leak ignited by an unknown source of ignition. You can find the civil report at ERAU and the FBI files in the FBI FOIA website.
The presence of the FBI & the military did provide great resources, and made it possible for this to be the most thorough investigation of an air loss ever. 95% of the plane was recovered, 230 victims were plucked out of the anonymity of a watery grave, tens of thousands of parts and fragments were pored over by metallurgists and explosives experts.
You should see an investigation of a Cessna prang with one killed. Usually the NTSB doesn't even send anybody, but has the FAA look into it, and bases its finding on the FAA report, unless it's odd. (I think most of us would agree that there is a national interest in finding the facts in a major airline crash that is greater than in studying why I did it if I stuff a 172 in the ocean).
Anyway, one of the things to come of this is better coordination between FBI and NTSB. I think the FBI Special Agents have a lot more respect for accident investigators now.
Now you also say: [FBI says] "we won't let you investigate the wreckage."
The wreckage remains sealed because of ongoing litigation, but pray tell why should FBI let unqualified people, pushing an agenda, in to see it? Their experience with Sanders was not exactly positive. We don't have the right to take Lee Harvey Oswald's gun to try out our JFK theories, either. We don't have the right to do our own autopsies on crime or accident victims. There are some things that have to be reserved to the people whose duty it is to do them.
FBI let NTSB, and its consultants, and the parties to the investigation -- the line, the unions, the manufacturers -- inspect the wreckage -- in all thousands of people. Not to mention the thousands who assisted in the recovery of wreckage and remains. If you are running a conspiracy that big, you might as well just hold a press conference and invite everybody.
And: "here is a video by the CIA that proves it was the center fuel tank."
The video purports to "prove" no such thing, it merely provides a visualization of the breakup sequence. There is a massive body opf evidence pointing at the centre fuel tank. The focus on the video by missile and bomb fans is hard to explain, unless they are (1) fixated on the CIA as a nexus of conspiracies, like Rivero and Ruppert, or (2) unable to confront evidence that doesn't come in Nintendo format.
Incidentally, the agency video shop has been used in other NTSB investigations, I just learnt.
d.o.l.
Criminal Number 18F