Plastic Bomb Downed 747, Investigators Find : British Cite ‘Conclusive Evidence’

LONDON — British investigators said Wednesday that they have “conclusive evidence” that a bomb, not structural failure, caused the midair breakup of a Pan American jumbo jet over southwestern Scotland last week, sending 259 passengers and crew to their deaths.

In simultaneous announcements here and in Lockerbie, the tiny Scottish village where the fiery wreckage rained down and killed at least 11 more people on the ground the night of Dec. 21, Britain’s Air Accidents Investigation Branch said that residue on pieces of the doomed Boeing 747 have been “positively identified” as resulting from “a high performance plastic explosive.”

‘International Dimensions’

The finding immediately triggered what a Scottish police official termed “a criminal inquiry of international dimensions.” John Boyd, chief constable for the area, told reporters in Lockerbie that the “mammoth” probe involves both Scotland Yard’s anti-terrorist branch and the FBI.

In Beverly Hills, the White House issued a brief written statement saying: “The FBI and the FAA are working closely with the British and Scottish authorities on the investigation. We are determined to find out who did it, using all available resources.”

But the conclusion came as a relief to the world’s airlines--more than 70 in at least 40 countries fly Boeing 747s. More than 700 of the planes are in service; another 100 are on order. And a verdict of structural failure in the Pan Am case might have led to the grounding of the entire fleet pending safety inspections.

The British investigators said it will take much more work to determine the nature of the bomb, how it got on board and where it was stored. However, a Transport Ministry source revealed that the authorities have already directed American flag carriers using British airports “to take added security measures with respect, particularly, to hold baggage.”

Traces on Luggage Pallet

Sabotage experts at the Defense Ministry’s elite Royal Armaments Research and Development Establishment clinched the bombing verdict when they found traces of the plastic explosive on two parts of the metal framework of a luggage pallet, the source noted.

Other physical evidence, including the wreckage trail on the ground, had previously led to speculation that an explosion in Flight 103’s forward luggage hold ripped the cockpit of the New York-bound aircraft from the fuselage as the jumbo jet cruised at 31,000 feet.

Such a sudden calamity may explain why the cockpit crew did not transmit a distress signal and the cockpit voice recorder showed no talk or reaction to any mishap.

The Transport Ministry source said it is “uncertain whether (the bomb) came on board here or in Frankfurt.”

Pan American World Airways Flight 103, bound for New York City, originated in Frankfurt, West Germany, aboard a smaller plane, a Boeing 727, then shifted to the jumbo during a stopover in London.

In either case, however, the bomb was not detected by a security system at the city’s main airport, Heathrow, which is said to be one of the most thorough and sophisticated in the world. Aviation experts here cautioned that while the bomb may have been smuggled on board in a suitcase, it could also have been planted by an airport employee on the payroll of a terrorist organization.

Opposition Calls

The opposition Labor Party called for a review of airport security as well as a “full and independent investigation” of the conduct of the Transport Ministry in connection with the Pan Am crash, which was the worst air disaster in British history.

Transport Ministry officials conceded last week that while they had been alerted by the U.S. Federal Aviation Administration to a pre-Christmas bomb threat against an unspecified Pan Am flight from Frankfurt, they did not pass on the warning to Heathrow Airport authorities. The threat was one of many received routinely, and they were satisfied with specially stringent security procedures already in place for American flag carriers, the officials said.

Neither British nor American officials alerted travelers to the threat, which was telephoned on Dec. 5 to the U.S. Embassy in Helsinki and passed along four days later to U.S. diplomatic missions abroad, American carriers serving Europe and friendly governments.

However, Finnish authorities and the FBI have discounted any connection between the phoned-in warning and the fate of Flight 103.

Michael Yardley, a terrorism expert and author quoted by the domestic Press Assn. news agency, speculated that the Pan Am bomb was “a large device, probably 10 to 20 kilos (22-44 pounds) of a plastic explosive like Semtex.”

Difficult to Detect

Semtex is a Czechoslovakian-produced plastic explosive used for military and industrial purposes. It is lightweight, odorless and difficult to detect.

Libyan leader Moammar Kadafi is believed to have obtained large quantities of the explosive, some of which he has allegedly passed on to the Irish Republican Army and extremist Palestinian groups.

Scotland Yard, the metropolitan London police force that is the nation’s largest and most sophisticated, stumbled upon a cache totaling a reported 150 pounds of Semtex a week ago in what they described as a major IRA bomb factory in south London. A 20-pound Semtex bomb was reportedly used by an IRA squad last August to reduce a brick army barracks in London to rubble, killing one soldier and injuring nine others.

No one has connected the IRA to the Pan Am bombing. Suspicion has been centered instead on radical Iranian or Palestinian groups.

More than 600 police, soldiers, and rescue specialists are still combing the countryside around Lockerbie searching for more wreckage and traces of 29 bodies still missing from the crash. Police spokesman Angus Kennedy said the remains of 241 victims have been recovered, although most have not yet been identified.

Authorities identified four more victims Wednesday, according to the Associated Press: Michael Joseph Doyle, 30, of Voorhees, N.J.; Robert Gerald Fortune, 40, of New Milford, N.J.; Sean Concannon, 16, of Banbury, England, and flight attendant Noelle Lindie Berti, 41, of Paris.

Police frogmen have joined the effort on the possibility that some victims and debris may have fallen into local lakes and reservoirs.

Searchers continued Wednesday to find more pieces of wreckage, and some of it is being funneled by the Air Accidents Investigation Branch to the special Defense Ministry laboratory in Kent.

Lengthy Examinations

“Each of these (items) will be subjected to lengthy chemical and metallurgical forensic examinations,” according to the branch’s official statement. “However, it has been established that two parts of the metal luggage pallet’s framework show conclusive evidence of a detonating high explosive. The explosive’s residues recovered from the debris have been positively identified and are consistent with the use of a high performance plastic explosive.”

The statement continued: “Other evidence collected by the AAIB, in particular that from the flight data recorder and the cockpit voice recorder and from the wreckage trail on the ground, has led to the preliminary conclusion that the explosion took place soon after the aircraft had crossed the Scottish border whilst it was in the cruise at 31,000 feet, and that this led directly to its destruction.

“Much investigative work remains to be done to establish the nature of the explosive device, what it was contained in, its location in the aircraft and the sequence of events immediately following its detonation.”

Earlier Wednesday, the Times of London reported that heat damage to the plastic lining of a cargo bay and metal slivers found embedded in the bodies of passengers also indicated that a bomb caused the air disaster. It attributed its report to unnamed crash experts.

An American official who requested anonymity, meanwhile, praised what was described as the extraordinarily open British attitude toward cooperation with their American counterparts in the investigation.

‘Working Hand in Glove’

In the past, according to this source, the British have sometimes been less than enthusiastic about such joint efforts. But this time “they have welcomed U.S. participation in its fullest.” Representatives of the two governments “have been working hand in glove,” the source said.

The White House statement, issued near where President Reagan is spending the Christmas-New Year holiday at his new home in Bel-Air and with friends in the Palm Springs area, said: “We have closely cooperated with the British investigation. We agree with the results of their investigation.”

The statement, issued by Deputy White House Press Secretary Leslye Arsht said Reagan was told of the British findings by his assistant for national security affairs, Lt. Gen. Colin L. Powell, during the morning.

In cooperating with British authorities, the FBI is exploring four avenues of investigation, the bureau’s director, William S. Sessions, told a press conference in Washington: Furnishing assistance in any forensic examination; assisting in the investigation of the cargo, crew and passengers of Flight 103; assisting with the FBI’s disaster squad in the identification of victims, and collecting intelligence in cooperation with international law enforcement and intelligence components.

“The investigation will be conducted in keeping with our objective of establishing the motive for this action--be it terrorism or other criminal actions,” Sessions said.

The FBI’s authority for taking part in the investigation is a section of the federal criminal code that outlaws interfering with or destroying U.S. aircraft traveling in foreign or interstate commerce. This law carries penalties of up to 20 years imprisonment and $100,000 in fines.

If terrorism is found to be the motive, the FBI also would have jurisdiction under a 1986 law against terrorist acts abroad against U.S. nationals. The law carries punishment of up to life in prison.

Sessions repeatedly emphasized that it “is unknown who is responsible.”

“We have no basis on which to suspect it definitely was terrorism,” Sessions said.

In pursuing non-terrorist, criminal possibilities, FBI officials said relatives and friends of the victims would be questioned about any information they might have on possible motives, such as collecting insurance or exacting revenge.

Times staff writers Ronald J. Ostrow, in Washington, and James Gerstenzang, in Beverly Hills, contributed to this article.