TWA crash: Still searching a year later

July 15, 1997
Web posted at: 10:10 a.m. EDT (1410 GMT)

From Correspondent Christine Negroni

(CNN) -- It has been nearly a year since TWA Flight 800 crashed off the coast of New York, killing all 230 people on board. Despite dramatic attempts to put together the puzzle of the July 17, 1996 crash, investigators are still not sure why it went down.

One theory is volatile fumes in the plane's nearly empty center fuel tank may have been heated to an explosive point by air conditioner units while the plane sat on the runway before takeoff. To test this theory, government investigators sent a specially equipped Boeing 747 on the first of a series of test flights this week.

The National Transportation Safety Board hopes to re-create the conditions under which Flight 800 flew. Electronic monitors mounted in the plane's center and wing fuel tanks will record data during the flights.

Search for clues frustrating

The underwater search to retrieve the victims and the plane was frustrating, and the search for the cause would be no less so. While the safety board concentrated on what it could learn from the plane's debris, hundreds of FBI agents swarmed over Long Island, checking out eyewitness reports of a light streaking toward the plane and acting on a collective gut feeling that the crash was a terrorist act.

"We had every reason to believe something criminal had happened," FBI Assistant Director Jim Kallstrom would later say.

Even NTSB Chairman Jim Hall admitted at a congressional hearing that he initially thought the crash would prove not an accident, but a deliberate attack, and that the investigation would be taken over by the FBI. "Like many Americans, I thought it might be a bomb," he said.

Science suggests non-criminal cause

But after investigators reconstructed 90 feet of fuselage, fired missiles at wreckage and set other test explosions, sophisticated science steered the investigation away from a criminal cause. Autopsies of the passengers showed no evidence that a bomb or missile had gone off inside the plane.

Instead, investigators found that the plane's air conditioning units, located directly below the fuel tank, had been running for three hours -- all the while, heating the vapors inside the tank. By the time it was airborne, there was an explosive brew in the belly of the plane.

Thirteen minutes after takeoff from New York's John F. Kennedy International Airport, the jetliner exploded in a fireball over the Atlantic Ocean.

"The plane essentially unzipped," Hall said, "creating a downward force that broke the backbone, or the keel beam, of the plane, and the nose separated, and all that happened quicker than I've been able to explain it. Simply seconds."

Airplane safety depends on keeping ignition sources away from the tank. Now, investigators hope to determine whether locating the air conditioning units so close to fuel tanks is safe.

The Federal Aviation Administration is also studying the possible hazards of allowing planes to fly with explosive vapors in their fuel tanks.