Diabolically Well-Planned: Pan Am's Flight 103

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For jittery air travelers, the news was decidedly mixed. No, the jumbo jet had not suddenly disintegrated in midair from metal fatigue. But, yes, there are people out there who are capable of planting bombs aboard passenger planes to blast them -- and hundreds of innocents -- out of the sky. When Britain's Department of Transport announced last week that investigators had found "conclusive evidence of a detonating high explosive" that shattered Pan Am Flight 103 at 31,000 ft. above Scotland, killing some 270 people, two questions took on a grim priority: Who did it? And why?

Working with unusual urgency, experts at a British army ordnance laboratory in Kent took only days to determine the cause of the crash. From wreckage recovered near the devastated rural town of Lockerbie, they examined a ripped suitcase, fabric from some passenger seats and fragments from a metal bin in which checked luggage was packed and then rolled into the cargo hold of the Pan Am 747 at London's Heathrow Airport. Two pieces of the container's framework were pitted and showed other signs that a "high-performance plastic explosive" had erupted near them. Scotland Yard's antiterrorism branch and the FBI jointly assumed the difficult task of finding out how the bomb got on the plane.

Engineers at Seattle's Boeing Co., makers of the 747, said the explosive almost certainly had been placed in the aircraft's forward baggage hold, just in front of the section where the wings are attached to the fuselage. They estimated that about 10 lbs. of a plastic explosive had in effect decapitated the 747, instantly severing the cockpit and part of the first-class cabin from the rest of the plane. Because the forward luggage compartment is next to the main electronics bay, the explosion instantaneously cut off all communications, electricity and flight controls, explaining why all systems went dead at the same moment. Declared a Boeing expert: "It was a diabolically well-planned event, handled by experts in knowledge of the aircraft, its structure, the flight plan -- the works."

The bomber's only mistake apparently was in timing. Terrorism experts assume that a timer had been set so that the charge would explode after the flight cleared the British Isles and was over water on its course to New York. If so, specific evidence of the sabotage would have been almost impossible to dredge up from the wintry Atlantic. But Flight 103 left Heathrow 25 minutes late. Anticipating such delays, terrorists have used barometers to start a timer only when a set air pressure has developed near the bomb. Since the cargo holds in a 747 are pressurized after takeoff along with the cabin, the barometer could detect this change and start the timer. If such a technique was used on Flight 103, it failed to postpone the blast until the aircraft was over water only because high-altitude winds caused the crew to take a northerly course over Scotland before heading west.