'In the Fokker-100, fuel lines run under the cabin floor, above the baggage compartments, from wing tanks to aft-mounted engines.'

He traced the route with his pointer, clicked to a close-up of a fuel line, then zoomed in on a fitting.

'Our structures team has found evidence of a fatigue crack in a fuel line fitting where it passes through the bulkhead at the rear of the baggage compartment. In al likelihood, this crack was generated by a flawed through-fitting acting as a stress riser.'

A magnified image of a hairline fracture filed the screen.

'Heat from the incandescent combustion in Mr. Lindenbaum's duffel aggravated the crack, alowing minute quantities of vaporized fuel to dissipate from the line into the hold.'

He brought up a dirty and discolored chunk of metal casting.

'Localized heat degradation, manifested in localized discoloration, is clearly recognizable on the fuel line at the point of failure due to heat exposure. I'l go to simulation now.'

Keys clicked, the screen went blank, then filed with an animation of an F-100 in flight. Time ticked in one-second increments at the top of the screen.

The Lindenbaum duffel could be seen high in the left rear of the baggage compartment, immediately below seats 23A and B. I watched it ooze from pink, to salmon, to red, a cold lump in the pit of my stomach.

'Incandescent combustion in the duffel,' Jackson narrated. 'A first ignition sequence.'

Pale blue specks began to seep from the bag.

'Smoke.'

The particles formed a fine, transparent mist.

'The baggage compartment is pressurized the same as the passenger cabin, meaning it is supplied with air containing an adequate proportion of oxygen. The significance is that there is a lot of warm air moving around down there.'

The mist slowly dispersed. Red colored the ends of the Lindenbaum suitcase.

'Though it was contained at first, the smoke eventualy spread from the duffel. The heat eventualy pierced, and then there was a development to laminar flaming combustion outside the duffel, igniting the suitcases on each side and giving off dense smoke.'

Tiny black dots appeared at a fuel line running along the inner wal of the baggage compartment. I stared, mesmerized, as the dots multiplied and slowly descended, or were entrained in the ambient air movement.

'Then began the second ignition sequence. When fuel began to dissipate out of the pressurized line, the quantity was so minute it vaporized and mixed with the air. As the fuel expanded in a vapor state it sank, since fuel fumes are heavier than ambient air. At that point an odor would have been present and easily detected.'

Traces of blue appeared in the passenger cabin.

'Smoke seeped into the cabin through the ventilation, heating, and air-conditioning system, and eventualy to the exterior via the pressurization outflow valve.'

I thought of Jean Bertrand. Had he noticed the odor? Seen the smoke?