The 747 had been flying smoothly through the winter sky, crossing into Scotland, when the conversation between the cockpit crew and flight controllers ended in mid-sentence. The cockpit voice recorder that captured the dialogue recorded a loud background noise that lasted 180 milliseconds, about the time it takes to blink an eye. Then the recorder lost power.

Inside luggage container AVE 4041 PA in the forward cargo hold, a battery had sent an electrical charge through wiring to ignite a fuse. The fuse's charge was minor, just enough to detonate about 12.25 to 14 ounces of Semtex that had been packed around it. The plastic explosive turned from solid to hot gas almost instantly, creating tremendously high pressure as the material expanded to occupy the space it needed in gaseous form. A spherical shock wave raced outward from the point of the detonation, shattering part of the base and outboard face of baggage container AVE 4041 PA. Fragments and heat from the blast pitted and scorched parts of that aluminum container and the outside of AVN 7511 PA, a fiberglass luggage container directly to the rear. The nearest section of the aircraft's frame buckled. The sphere of the blast wave grew larger; intersecting the skin of the aircraft after traveling only about 25 inches. It punched a hole in the fuselage about 18 to 20 inches in diameter, barely a pinprick in the skin of a jet 225 feet long. Only milliseconds had passed since the bomb's detonation.

Blasting the hole spent only a portion of the Semtex's force. The fuselage reflected a substantial shock wave back toward the point where the explo-sion had originated. When these reflected waves crashed head-on with the pulses from the blast itself, a phenomenon known as a Mach stem shock wave resulted. The interaction of the blast and reflected waves created a powerful offspring that sped along the curved surfaces of the inside of the fuselage skin like a race car through a banked turn. This Mach stem wave, a hybrid of the direct and reflected shock waves, probably was 25 percent faster than, and twice as powerful as, the waves from the explosion itself. Mach stem waves normally shoot off in odd directions, depending on the configuration of the reflective surfaces. But on a Boeing 747 there are ready-made conduits to transport Mach stem waves-in effect, to channel and intensify their effects. The Mach stem waves raced away in two main directions: down into the belly underneath the baggage containers and up the left side of the plane in the gap between the baggage containers and the inside of the fuselage wall. The power of these waves would doom the aircraft.

The Mach stem waves created tremendous overpressure in various cavi-ties of the aircraft, some far away from the point where the bomb exploded. Consequently, at about the same time that the direct effect of the blast punched the eighteen-inch hole in the fuselage, overpressures from Mach stem waves peeled off a section of the 747,5 roof several feet above the point of detonation. Similarly these waves gouged a hole through the thick skin in the belly of the plane. The continuing high pressure forced thejagged edges of the holes to petal out. As the cracks spread, the holes grew bigger The 747,5 air-conditioning system channeled shock waves into the cabin, where they bounced off galleys, overhead luggage racks, and other hard surfaces to bombard first-class passengers with jolts from several sides.

A cloud of high-pressure gas spreading out at supersonic speed followed closely behind the shock waves. This gas sustained the high pressures in areas that had just been pummeled by explosive shock. The bomb's effects were enhanced by the difference in conditions inside the plane, where air pressure was kept at breathable levels, and those outside the fuselage, where the air pressure at thirty-one thousand feet was only about one-quarter of what it is at sea level. In an instant huge chunks of the aircraft above and below the window line between the cockpit and wings were gone, torn away by the blast and by the resistance of the wind rushing past.

The blast warped sections of the plane containing the cables that are used to control the flaps and tail. The explosion moved the cables so that the aircraft dived and rolled to the left. By now the explosion had knocked out power, thrusting the cabin into darkness. The front of the plane continued to disintegrate from the top and bottom, leaving intact the windows on the side of the fuselage and the floor. The floor which had been reinforced to carry military cargo in wartime, gave way next. When the plane dived and rolled to the left, the reinforcing belt that held the row of windows along the left side failed. The cockpit and forward section of the fuselage broke away, deflecting up and to the right. As this breakaway section peeled back, the right window belt that held it to the rest of the fuselage snapped, and as the nose cone tore free, it struck the No.3 engine, knocking it from the right wing. Chunks of the forward fuselage continued to break away, peppering the tail on their way past until the tail structure was a jagged silhouette. Three seconds after the explosion, the fuselage, cockpit, and No.3 engine were falling separately.

The fuselage was an open cylinder, hopelessly nonaerodynamic. Tornado-force winds tore down the aisles, stripping clothing off the backs of passengers and flight attendants, turning drink carts into lethal projec-tiles and filling the air with sharp, deadly pieces of shrapnel. The wind and the rending of metal created a tremendous roar. Some passengers were thrown to the rear. Others, tossed out into the night, joined luggage and other pieces of the plane to form a ghostly caravan that swept through the moonlit troposphere at 499mph. These passengers were battered by a 130-mile-an-hour crosswind in an air temperature that was fifty degrees below zero Fahrenheit.

In the instant that the sealed fuselage broke apart, the air pressure inside the cabin plummeted to equal that of the atmosphere outside. Suddenly subjected to the lower air pressure, gases inside passengers' bodies ex-panded to four times their normal volume. Most of the passengers found themselves fighting for breath. Expanding gases caused their lungs to swell and then collapse, driving the oxygen out of their system. Fierce winds slaramed into their face and chest, making it difficult to breathe.

As the plane descended to nineteen thousand feet, gravity overcame forward momentum and the fall became almost vertical. The tail fin disintegrated. Tremendous pressures tore at the structure, pulling the remaining three engines from the wings. The fuselage broke into pieces, separating from the wings. Different chunks of the aircraft descended at different speeds. The wings, slowed least by the atmosphere because of their shape, sliced downward at an accelerating rate. They reached their destination first, still laden with two hundred thousand pounds of fuel.