Errant Navy missiles? A stray spark? A meteorite?
Nearly nine months after TWA Flight 800 exploded off Long Island, the cause of the crash that killed all 230 aboard remains elusive. But investigators may be closing on an answer.
With some 90 percent of the 170-ton aircraft recovered and identified, and about 98 percent recovered, federal investigators definitely know the center fuel tank exploded, causing the aircraft to split in two. They do not know, however, what ignited the vapors in the tank. The main theories haven't changed since July 17: a bomb, a missile, or a mechanical failure.
But this week, new light could be shed on the source of ignition. "The 3-D mock-up is nearly finished, so we are entering an analytical phase," says James Kallstrom, the FBI official in charge of the criminal investigation.
A 92-foot section of the plane from the center fuel tank (in the belly of the plane between the wings) to the cockpit is nearly complete. Forensic scientists will then look for identifying patterns - examining "the orientation of every hole, every penetration, and missing piece," says Mr. Kallstrom.
Forensic scientists know a lot about what metal looks like after it's been destroyed by a bomb, he says. But little is known about missile damage. So investigators are collecting what information is available in one data base.
The FBI and the National Transportation Safety Board have gone to extraordinary lengths to solve this mystery in what is now the largest and most expensive aviation investigation ever. Including the recovery of the plane, the NTSB has spent $27 million above and beyond its normal $38 million annual budget. The FBI has cut back from 500 to about 50 agents, but hasn't tallied the cost yet. It's "in the millions," says Kallstrom.
The NTSB - charged with finding causes of airline crashes and recommending ways to prevent them - continues to conduct a battery of tests from California to Britain. Researchers at the California Institute of Technology are studying the properties of Jet-A fuel. Researchers at Wright-Patterson Air Force Base in Dayton, Ohio, are running static tests to determine if a static build-up in the fuel tank could produce enough spark to ignite the tank.
The NTSB also is working with the British government, which is conducting tests on an older Boeing 747. They intend to set off small charges in the cargo hold to determine how a bomb could be contained. The NTSB is interested in what the blast sounds like on the cockpit voice recorder.
In December, the NTSB made several safety recommendations aimed at preventing center fuel tanks from exploding, no matter the source of ignition. Among other things, they call for the center fuel tanks be kept full or filled with another gas such as nitrogen.
The FBI continues to follow up on civilian reports and claims, ranging from friendly fire to the far out. And Kallstrom contends, as he has from the beginning, that there is no possibility that friendly fire brought down the TWA jet.
A hearing will be held in New York April 16 to determine how a former airline pilot obtained a copy of an FAA radar tape that he contends proves a missile hit Flight 800 (the FBI and NTSB discount the claim).
Irving Itzkan, a physicist at Massachusetts Institute of Technology in Cambridge says it is possible that a meteorite brought down the plane. He admits the probability is remote (about 1 percent per century). He says about three meteorites hit the earth each day - usually in very remote places.
But a meteorite between the size of a baseball and basketball traveling at five to 10 times the speed of sound could have pierced the plane and ignited the center fuel tank. The meteorite would have vaporized the metal, Dr. Itzkan contends.
Privately, NTSB officials worry that it could have been a meteorite or some other natural act that may not leave clear evidence.
Kallstrom calls such concerns "baloney." Metallurgists would know if a high-velocity object hit the plane, he says, and they can account for missile or bomb damage.