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center. It was a pilot’s cap, with a stripe for a captain, so it probably belonged to one of the backup crew. If this plane carried a backup crew; she didn’t know that yet.
    “Oh dear me this is awful just awful.”
    She heard the distinctive monotone, and looked up to see Doug Doherty, the structural engineer, striding into the aft cabin.
    “What did they do to my beautiful plane?” he moaned. Then he saw Casey. “You know what this is, don’t you. It’s not turbulence. They were
porpoising
.”
    “Maybe,” Casey said. “Porpoising” was the term for a series of dives and climbs. Like a porpoise leaping in water.
    “Oh yes,” Doherty said, gloomily. “That’s what happened. They lost control. Terrible, just terrible …”
    One of the paramedics said, “Mr. Doherty?”
    Doherty looked over. “Oh don’t tell me,” he said. “
This
is where the guy got wedged?”
    “Yes, sir …”
    “Wouldn’t you know,” he said, gloomily, moving closer. “It had to be the aft bulkhead. Right where every flight-critical system comes together to—okay, let me see. What is it, his foot?”
    “Yes, sir.” They shone the light for him. Doherty pushed up against the body, which swayed in the harness.
    “Can you hold him? Okay … anybody got a knife or something? You probably don’t but—”
    One of the paramedics gave him a pair of scissors, and Doherty began to 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?”
    You’ll 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