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cut Bits of silver insulation floated to the ground. Doherty cut again and again, his hand moving quickly. Finally he stopped. "Okay. He missed the A59 cable run. He missed the A47 cable run. He's left of the hydraulic lines, left of the avionics pack... Okay, I can't see he hurt the plane in any way."
    The paramedics, holding the dead body, stared at Doherty. One of them said, "Can we cut him out, sir?"
    Doherty was still looking intently. "What? Oh yeah sure. Cut him out"
    He stepped back, and the paramedics applied the big metal jaws to the upper portion of the plane. They wedged the jaws between the overhead luggage bins and the ceiling, then opened them. There was a loud cracking sound as the plastic broke.
    Doherty turned away. "I can't watch," he said. "I can't watch them tear up my beautiful aircraft."
    He headed back to the nose. The paramedics stared as he left
    Richman came back, looking slightly embarrassed. He pointed out the windows. "What're those guys doing on the wing?"
    Casey bent down, looked through the windows at the engineers on the wing. "They're inspecting the slats," she said. "Leading edge control surfaces."
    "And what do slats do?"

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    You'II have to start him from the beginning.
    Casey said, "You know anything about aerodynamics? No? Well, an aircraft flies because of the shape of the wing." The wing looked simple, she explained, but it was actually the most complicated physical component of the aircraft, and it took the longest to build. By comparison, the fuse—the fuselage—was simple, just a lot of round barrels riveted together. And the tail was just a fixed vertical vane, with control surfaces. But a wing was a work of art. Nearly two hundred feet long, it was incredibly strong, capable of bearing the weight of the plane. But at the same time, precisely shaped to within a hundredth of an inch.
    "The shape," Casey said, "is what's crucial: it's curved on top, flat on the bottom. That means air going across the top of the wing has to move faster, and because of Bernoulli's principle—"
    "I went to law school," he reminded her.
    "Bernoulli's principle says the faster a gas moves, the lower its pressure. So the pressure within a moving stream is less than the air surrounding it" she said. "Since air moves faster across the top of the wing, it creates a vacuum which sucks the wing upward. The wing is strong enough to support the fuselage, so the whole plane is lifted up. That's what makes a plane fly."
    "Okay.. ."
    "Now. Two factors determine how much lift is created— the speed the wing moves through the air, and the amount of curvature. The greater the curvature, the greater the lift."
    "Okay."
    "When the wing is moving fast, during flight, going maybe point eight Mach, it doesn't need much curvature. It actually wants to be almost flat. But when the aircraft is moving slower, during takeoff and landing, the wing needs greater curvature to maintain lift. So, at those times we increase the curvature, by extending sections in the front and back—flaps at the back, and slats at the leading edge."
    "Slats are like flaps, but in the front?"
    "Right."
    "I never noticed them before," Richman said, looking out the window.
    "Smaller planes don't have them," Casey said. "But this aircraft weighs close to three-quarters of a million pounds, fully loaded. You've got to have slats on a plane this size."
    As they watched, the first of the slats moved outward, then tilted down. The men on the wing stuck their hands in their pockets and watched.
    Richman said, "Why are the slats so important?"
    "Because," Casey said, "one possible cause of 'turbulence' is slat extension in mid flight.
    Remember at cruise speed, the wing should be almost flat. If the slats extend, the plane may become unstable."
    "And what would make the slats extend?"
    "Pilot error," Casey said. "That's the usual cause."

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    "But supposedly this plane had a very good pilot."
    "Right. Supposedly."
    "And if it wasn't pilot error?"
    She