While there may be no quick answers to the tragedy of Pan Am Flight 103, the wreckage scattered across the Scottish countryside has left enough clues to make it virtually certain the cause will be found, aviation experts said Friday.

As more information surfaced, specialists noted the similarities between Wednesday's crash of the Boeing 747 in Scotland that killed all 258 people aboard and at least 22 on the ground, and the crash three years ago of an Air India jumbo jet off the Irish coast.Indian officials, after months of retrieving wreckage from the ocean floor, concluded that a bomb exploded aboard the Air India jetliner. An explosion is widely believed to have caused the Pan Am plane to crash, although no conclusive evidence of a bombing has yet surfaced.

Both the Pan Am and Air India planes were cruising routinely at 31,000 feet and suddenly disappeared from radar. In neither case did the flight crew declare an emergency or make any radio contact with air traffic control. In both cases, the planes broke up in the air, scattering wreckage over five or more miles.

In both crashes, the recording from the cockpit gave no indication the pilots were aware of anything unusual, but contained a muffled sound in the final split second of tape.

That sound became crucial in the Air India investigation. The final report on the accident concluded: "From the sounds found recorded on the CVR (cockpit voice recorder) and the (air traffic control) tapes, it appears that an explosion had occurred on board the aircraft."

Authorities in Scotland announced Friday that a preliminary review of the CVR tape from Pan Am Flight 103 also ends with a muffled sound a fraction of a second before the recorder went dead.

"There is nothing in the conversation (of the pilots) to indicate anything was wrong," said a British spokesman, reminiscent of the Air India findings.

Paul McKie, spokesman for the Department of Transport, cautioned that further analysis will be required before it can be determined what the noise might be and warned not "to jump to any conclusions."

More sophisticated spectrographic examination of the tape likely will provide a better clue as to whether the sound is an explosion from a bomb, or a breakup of the aircraft because of a sudden decompression. Similar sounds have been heard on CVR taps in other accidents when aircraft experienced major structural failures, officials said.

U.S. aviation experts, including several who have been involved in investigating scores of air disasters, are confident the answers will be found.> Experts noted in interviews that the Pam Am crash investigators have some advantages.

For example:

-While the crash caused an inferno in the small Scottish farming town of Lockerbie, destroying a row of houses, most of the aircraft - with the exception of a destroyed right wing whose fuel tank exploded - appeared to have escaped serious fire damage.

In many crashes where a plane remains intact and bursts into flames, critical clues are lost because of the intense heat that bends metal and destroys evidence.> -The wreckage, although strewn across the countryside, is not - as was the case of Air India - in hundreds of feet of water and exposed to elements that could destroy critical evidence.

-The cockpit voice recorder and flight data recorder appear to be in good shape.> In the coming days, investigators will pay close attention to how parts of the aircraft are bent, tangled and singed and whether there is evidence of a chemical residue normally left by an explosive. They also will search for fragments that might have been used as a detonator.

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