Probers Study Eyewitness Accounts, Radar Printouts

Federal investigators, seeking to understand what turned TWA Flight 800 into a flying fireball, have begun poring over a wealth of evidence--from vivid eyewitness reports to radar printouts and pieces of the plane drawn from the sea.

No physical evidence has yet surfaced to indicate that Flight 800 was brought down by a terrorist bomb or a missile.

But already, some FBI, intelligence and aviation officials have begun to draw an initial hypothesis.

“The circumstantial evidence all points to an explosive device that was probably deliberate,” said a senior law enforcement official. “The job will be proving that it wasn’t terrorism.”

The cause might also have been a catastrophic mechanical problem, such as an engine failure. Or, it might have been an airborne object that struck the plane, officials said.

One key piece of evidence will be the plane’s data recorders. The explosion of a bomb on board would produce a “signature sound,” House Minority Leader Richard A. Gephardt (D-Mo.) said after a briefing by investigators.

In addition to seeking the “black box” recorders, officials in many parts of the government are combing intelligence reports, including electronic intercepts, for possible motives for targeting an American aircraft. So far, however, no conspicuous possibilities have emerged, officials said.

“No one has a specific hypothesis at this stage” about who might have committed an attack, a counterterrorism official said.

And despite two post-crash claims of responsibility, U.S. officials said they had received no specific recent threats against TWA or credible general terrorism alerts inside the United States.

Pentagon spokesman Kenneth Bacon said there had been a “significant increase” in the number of recent threats against American interests in Saudi Arabia, Bosnia and elsewhere abroad. But all appeared tied to local issues, and none appeared linked to the TWA crash.

Terrorism experts outside the government were also puzzled. “There are a few groups with grudges, but there are no obvious reasons or motives,” said Magnus Ranstorp, an expert at the Center for Terrorism and Political Violence at St. Andrews University in Scotland.

But several alternative explanations already appear to have been ruled out by circumstances. The Boeing 747 is among the safest in the world. The crew included veteran pilots with solid records. The weather was clear. There were no Mayday calls from the cockpit indicating mechanical problems.

Aviation officials said Thursday that they had found no evidence of another plane in the vicinity and that no aircraft were missing--appearing to rule out the chance of a collision.

The takeoff of TWA Flight 800 was monitored on radar, and officials said Thursday that they were poring over second-by-second printouts for anything else in the skies. Officials tended to downplay early reports of a mysterious “blip” on the radar.

And the sudden and spectacular explosion, with some eyewitnesses reporting a breakup in midair, suggested that if a mechanical failure was the cause, it must have been an extraordinary one.

Some experts suggested a catastrophic engine failure might have sufficed to cause the tragedy. Others ruled even that out.

“This plane would not break up in flight,” said Paul Czysz, a former McDonnell Douglas engineer who teaches aerospace engineering at St. Louis University. “The 747 can lose pieces and still fly. It had to be something external--an explosive device, something blowing up in the cargo hold or something like a Stinger missile.”

National Transportation Safety Board officials said the plane was flying at roughly 8,000 feet at the time of the explosion. That would, at least theoretically, be within the range of a shoulder-fired missile--assuming the missile was fired from a boat under the flight path.

Pentagon officials urged caution in speculating about missiles, but said that such weapons have a range of about 10,000 feet if fired vertically and 18,000 feet if fired parallel to the ground.

Surface-to-air missiles “are not that easy to detect,” Czysz said. “[They] give off a pale blue light in flight, but if you don’t see the initial flash you wouldn’t necessarily spot it.”

As they seek clues on where to look, experts speculated that revenge for a variety of recent counterterrorism successes could be a possible motive for an attack.

The FBI has been concerned in the past, for example, about a backlash from the 1995 conviction of 10 persons for conspiring to bomb the United Nations and other New York landmarks.

Currently in New York, Ramzi Ahmed Yousef, who was captured in Pakistan and whisked back to the United States by the FBI, is on trial for plotting to blow up several Delta, Northwest and United flights to the United States from the Far East. Yousef, who is acting as his own defense attorney, is also due to face a second trial this fall on charges of masterminding the 1993 bombing of the World Trade Center.

Prosecutors allege that Yousef and other conspirators had planned to assemble a bomb while on a U.S. plane--smuggling liquid explosives onboard in contact lens solution bottles. The bomb would then have been exploded with watch timers--a formula he used successfully aboard a Philippine Airlines plane in 1994.

Experts ranked mechanical failure as by far the least likely explanation for the crash. The rugged and reliable 747, the world’s largest passenger aircraft, entered service in 1970 and remains the prime transoceanic jet. The TWA jetliner that exploded Wednesday had its inaugural flight in 1971.

“This has nothing to do with the age of the aircraft,” said Aaron Gellman of the Northwestern University’s Transportation Center. “Despite its problem, TWA has maintained its planes very well. Remember, this is not a new airline. It has very experienced people.”

Two of the four deadliest 747 incidents were traced to terrorism--the 1988 Pan Am bombing over Lockerbie, Scotland, that killed 270 people and the 1985 Air India midair bombing off the Irish coast, killing 329.

Only two of the five was an accident. In 1985, the pressured bulkhead of a Japan Airlines 747 blew out and took away the plane’s tailfin, killing 520. And in 1977, a KLM 747 and a Pan Am 747 collided on the ground in the Canary Islands, killing 582.

“As far as I know, there has never been uncontained engine failure on a 747,” Czysz said. “Even when they have tested them by putting an explosive inside the engine, the failure has been contained” in the engine shell.

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