NEW YORK — Five months into the most intensive investigation of an air crash in US history, the FBI's chief agent on the case says the cause of the midair explosion on TWA Flight 800 is still proving elusive - frustratingly so.
To be sure, investigators have collected a lot of pieces of the puzzle - including no fewer than 30,000 fragments of the plane fished from the fathoms off New York. But the recovery effort has not yet yielded the vital forensic proof investigators evidently need before they will say which of their original theories - a bomb, a missile, or a mechanical failure - explains the crash.
In fact, the cause may even be more complex than those three scenarios suggest. In an interview in his Manhattan office, James Kallstrom, assistant director of the FBI, now alludes to "some subsets of those kinds of things," indicating that the investigation team is broadening rather than narrowing its scope.
Mr. Kallstrom declined to "speculate" what those "subsets" might be, but his comments underscore how difficult it can be to pinpoint the cause of an air crash - even though scientists across the country are micro-inspecting every shard of wreckage and 70 full-time FBI agents continue working the case alongside 20 National Transportation Safety Board officials.
"We don't have any forensic, or scientific, evidence that tells us what happened," says Kallstrom, who spends at least half of every work day on this investigation.
That, to him, is the most frustrating thing about the case. He says it is probably a "function of my optimism." He had hoped to find that evidence in the "first 2 percent, not the last 2 percent," of wreckage retrieved.
On the intelligence front
While recovery and analysis of the aircraft have received the most attention, behind the scenes the investigation is continuing on several other fronts, including intelligence gathering. While it's conceivable that a tragedy such as TWA Flight 800 could be solved solely by intelligence sources - from spy satellites that eavesdrop around the world to undercover and sting operations - Kallstrom says, "It's not likely at this point that we're going to reach a conclusive position based on that type of information." The intelligence on this case, he insists, "is fairly quiet."
The investigation is moving forward on three other fronts.
Kallstrom says scallopers will continue scraping the ocean floor with their nets for at least another month or until they stop finding pieces. They intend to expand their search westward toward John F. Kennedy Airport.
"My hope is that ... there's a piece coming out of the water, out of the nets right now," Kallstrom says earnestly. "This second somebody is looking at it, and it's either a fuel pump they've been looking for that's all shorted out, or it is a piece of the fuselage or center fuel tank that has a long blast, or a hole that's caused by a rocket, or pitting or scarring" of the metal that would enable scientists to determine the cause.
The second aspect of the investigation is to build a mock-up of TWA 800, as investigators did with Pan Am Flight 103 after it exploded over Lockerbie, Scotland, in December 1988. (Photos of two Libyans deemed responsible for planting a bomb on the Pan Am flight appear on the FBI's 10 Most Wanted list posted outside Kallstrom's office.)
The FBI is now in the process of hiring a contractor to build the mock-up. A "skin" of the plane will be built out of plywood. Then the 30,000 or so pieces - from tiny, spaghetti-like wires to huge hunks of metal - will be applied to the skin.
"It's possible that by reassembling a portion of the airplane that it will sort of talk to us," Kallstrom explains. He says investigators know the chain of events that occurred after the center fuel tank exploded, but they don't know if that was the first explosion. "It [the wreckage] won't talk to us when it's lying in a pile. But maybe when it's put in a mock-up like the Pan Am 103 was, it will."
Finally, the National Transportation Safety Board is trying to arrange to blow up a center fuel tank on another Boeing 747. "Boeing has basically said that that fuel tank, with that amount of fuel in it, at that temperature, and at that altitude, would not be able to create enough pounds per square inch [of pressure] to cause the kind of damage we see to the fuel tank," Kallstrom says. "If what they say is true, that's significant. We need to know that."
In the painstaking process of trying to determine what could possibly make an aircraft explode in midair and without warning to the pilots, investigators have posited theory after theory - only to have them knocked down. For example, the early identification of chemical traces - like those that cause high-level explosions - was heralded as a breakthrough in the case. But it was later discounted when the FBI learned the plane had been previously used for a bomb-sniffing dog exercise in which the same chemicals were present.
Kallstrom says that in his 26-year career with the FBI, he has investigated a lot of big - and very sad - cases. But, for him, nothing compares with this one in terms of scope and public reaction.
"From the standpoint of the tragedy, emotions, the loss of life, the public scrutiny," this is by far the most significant.
He says the FBI will continue its dual investigation with the National Transportation Safety Board until the finish. And he remains confident that the cause of the crash will be found.
"Whether it's a week from now or a year from now, I think we'll know," says the former Marine, who served a tour during the Vietnam War.
Living the investigation
Still, the investigation has taken its toll on the people who've been closest to it. Kallstrom says his daughter came home from high school last week and said she'd like to go to Spain next summer with her Spanish club. He told her absolutely not, a reaction to the fact that 16 high school French club students were aboard TWA 800.
"I think people are thinking about things they never really thought about before," he says, referring to his own reaction as well as the fact that he's confronted continually by people who express to him their newborn fears of flying.
Kallstrom says he's learned lessons from this investigation. "We know an awful lot more about underwater recovery," he says grimly. "I hope we never have to put that experience to work again."
The other lesson, he says, is one that he continues to learn: patience. "Think things through. Don't jump to conclusions."