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All 230 people aboard TWA Flight 800 died when the plane exploded over the Atlantic minutes after take-off from New York's John F. Kennedy airport in 1996.
After a four-year investigation, which included scouring the ocean to piece together most of the jumbo jet, the National Transportation Safety Board said the cause was a spark from bad wiring that set off fuel tank vapors.
Almost two decades later, six retired members of that investigative team are changing their story in a new documentary, "TWA Flight 800."
The film claims the fuel tank theory is bogus and that an explosion outside of the plane brought it down.
Former, retired investigators are now suggesting there was a cover-up, and that they were directed to say the crash was an accident.
"I think it's a bunch of bull crap," said former FBI assistant director James Kallstrom, who headed the criminal probe after the crash.
"It seems like they've comfortably waited until they have their pensions before they became whistleblowers," he said.
"We did an exhaustive investigation. I had 1,000 agents assigned at the peak. And we took very seriously the idea that a missile could have shot down the plane. You know, 747s don't blow up in fireballs that can be seen 40 miles away," said Kallstrom.
Kallstrom said the investigation looked into whether it could have been terrorism five years before jetliners were used as missiles in the al Qaeda attacks on New York and Washington.
"We used all the assets of the United States, all the missile experts in the military. We shot missiles at planes so we could study, you know, what kind of damage they did to the aluminum frames," said Kallstrom.
The team spent a fortune recovering most of the wreckage, said Kallstrom, twice getting permission from the White House to continue investigating the crash.
"I'm very, very confident that we had enough of that airplane to make the judgment that no criminal intervention" brought down the aircraft, he said.
In 1996, ABC reporter Pierre Salinger said he had a government document – said to be from French intelligence - claiming that Navy gunners accidentally shot down the plane while conducting missile tests.
"I'm being kind when I tell you that he was out of his mind," Kallstrom said of Salinger.
Nevertheless, the investigation looked at every military asset in the area, and interviewed every member of the USS Normandy, which was out of range of the TWA Flight 800 by about 200 miles, said Kallstrom.
"It's just a preposterous thing to say. And it hurts the families," said Kallstrom. "That's the thing that irritates me about this thing now, coming forward. You know, it's basically B.S., in my view. And the families have to go through this whole thing."