"Any good?"

"Average. He's got about thirty hours."

On the closed-circuit video screen, Casey saw a man in his mid thirties, sitting in the pilot's seat of the simulator.

"And where is he now?" Felix said.

"Uh, let's see," the instructor said, consulting his panels. "He's over the mid-Atlantic, FL three-thirty, point eight Mach."

"Good," Felix said. "So he's at thirty-three thousand feet, eight-tenths the speed of sound. He's been there awhile, and everything seems to be fine. He's relaxed, maybe a little lazy."

"Yes, sir."

"Good. Deploy Mr. Ingram's slats."

The instructor reached over and pushed a button.

Felix turned to Casey. "Watch carefully, please."

On the video screen, the pilot remained casual, unconcerned. But a few seconds later, he leaned forward, suddenly alert, frowning at his controls.

Felix pointed to the instructor's console, and the array of screens. "Here you can see what he is seeing. On his Flight Management display, the slats indicator is flashing. And he's noticed it. Meanwhile, you see the plane gives a slight nose up…"

The hydraulics whirred, and the big cone of the simulator tilted upward a few degrees.

"Mr. Ingram now checks his slats lever, as he should. He finds it is up and locked, which is puzzling, since it means he has an uncommanded slats deploy…"

The simulator remained tilted up.

"So Mr. Ingram is thinking it over. He has plenty of time to decide what to do. The aircraft is quite stable on autopilot Let's see what he decides. Ah. He decides to play with his controls. He pulls the slats lever down, then up… He's trying to clear the warning. But that doesn't change anything. So. He now realizes he has a system problem on his aircraft. But he remains calm. He's still thinking… What will he do?… He changes the autopilot params… he descends to a lower altitude, and reduces his airspeed… absolutely correct… He is still in the nose-up attitude, but now at more favorable conditions of altitude and speed. He decides to try the slats lever again…"

The instructor said, "Should I let him off the hook?'

"Why not?" Felix said "I believe we have made the point."

The instructor punched a button. The simulator tilted back to level.

"And so," Felix said, "Mr. Ingram is restored to normal flight. He makes a note of his problem for the maintenance crews, and he continues on his way to London."

"But he stayed in the autopilot" Casey said. "What if he went out of it?"

"Why should he do that? He's in cruise flight; the autopilot has been operating the plane for at least half an hour."

"But suppose he did."

Felix shrugged, turned to the instructor. "Fail his autopilot."

"Yes, sir."

An audible alarm sounded. On the video screen, they saw the pilot look at the controls and take the stick in his hands. The audible alarm ended; the cockpit became silent. The pilot continued to hold the stick.

"Is he flying the plane now?" Felix asked.

"Yes, sir," the instructor said. "He's at FL two-ninety, point seven-one Mach, with autopilot disabled."

"Okay," Felix said. "Deploy his slats."

The instructor pushed a button.

On the systems monitor in the training console, the slats warning flashed, first amber, then white. Casey looked at the adjacent video screen and saw the pilot leaning forward. He had noticed the warning in the cockpit.

"Now," Felix said. "Once again we see the aircraft nose-up, but this time Mr. Ingram must control it himself… So he brings the stick back… very slightly, very delicately… Good… and now he is stable."

He turned to Casey. "You see?" He shrugged. "It is very puzzling. Whatever happened to that Transpacific flight, it cannot be the slats. And not thrusters either. In either case, the autopilot will compensate and maintain control. I tell you, Casey, what happened to that aircraft is a mystery."

Back in the sunlight, Felix walked over to his Jeep, with a surfboard on top. "I have a new Henley board," he said. "Like to see it?"

"Felix," she said. "Marder is starting to scream."

"So? Let him. He enjoys it."

"What do you think happened to 545?"

"Well. Let us be frank. Flight characteristics of an N-22 are such that if slats deploy at cruise speed, and the captain goes out of the autopilot the aircraft is rather sensitive. You remember, Casey. You did the study on it, three years ago. Right after we made the final fix on the slats."

"That's right" she said, thinking back. "We put together a special team to review flight stability issues on the N-22. But we concluded there wasn't a control-sensitivity problem, Felix."

"And you were correct" Felix said. "There is no problem. All modern aircraft maintain flight stability with computers. A jet fighter cannot be flown at all without computers. Fighters are inherently unstable. Commercial transports are less sensitive, but even so, computers shift fuel, adjust attitude, adjust CG, adjust thrust on the engines. Moment to moment the computers continuously make small changes, to stabilize the aircraft."

"Yes," Casey said, "but the planes can be flown out of autopilot as well."

"Absolutely," Felix said. "And we train our captains to do that. Because the aircraft is sensitive, when the nose goes up, the captain must very gently bring it back again. If he corrects too strongly, the plane noses over. In that case he must pull up, but again, very gently, or he is likely to overcorrect, so the plane would climb sharply then nose down once more. And this is precisely the pattern that occurred on the Transpacific flight."

"You're saying it was pilot error."

"Ordinarily I would think so, except the pilot was John Chang."

"He's a good pilot?'

"No," Felix said. "John Chang is a superb pilot. I see a lot of pilots here, and some are truly gifted. It's more than quick reflexes and knowledge and experience. It's more than skill. It's a kind of instinct. John Chang is one of the five or six best captains I have ever trained on this aircraft, Casey. So whatever happened to Flight 545, it cannot be pilot error. Not with John Chang in the chair. I am sorry, but in this case, it has to be a problem with the aircraft, Casey. It has to be that aircraft."

As they walked back across the vast parking lot, Casey was lost in thought.

"So," Richman said, after a while. "Where are we?"

"Nowhere."

No matter how she put the evidence together, that was the conclusion she came to. They had nothing solid so far. The pilot had said it was turbulence, but it wasn't turbulence. A passenger gave a story consistent with slats deployment, but slats deployment couldn't explain the terrible damage to the passengers. The stewardess said the captain fought the autopilot, which Trung said only an incompetent captain would do. Felix said the captain was superb.

Nowhere.

They were nowhere.

Beside her, Richman trudged along, not saying anything. He had been quiet all morning. It was as if the puzzle of Flight 545, so intriguing to him yesterday, had now proven too complex.

But Casey was not discouraged. She had come to this point many times before. It was no surprise the early evidence appeared to conflict. Because aircraft accidents were rarely caused by a single event or error. The IR teams expected to find event cascades: one thing leading to another, and then another. In the end, the final story would be complex: a system failed; a pilot responded; the aircraft reacted unexpectedly, and the plane got in trouble.

Always a cascade.

A long chain of small errors and minor mishaps.

She heard the whine of a jet. Looking up, she saw a Norton widebody silhouetted against the sun. As it passed over her, she saw the yellow Transpacific insignia on the tail. It was the ferry flight from LAX. The big jet landed gently, puffed smoke at the wheels, and headed toward Maintenance Hangar 5.