Callaway looked down at his hands, said nothing.
Back in the cockpit, Zariah was working the fuel imbalance. With the crossfeed valve open, she'd been slowly correcting the difference between the left and right tanks, but the process was sluggish. Whoever had introduced the restriction in the left fuel control unit had effectively slowed the left tank's consumption rate, which meant fuel was pooling on the left side while the right burned down faster. Left uncorrected, the weight asymmetry would worsen her roll tendency and add to the structural stress on the airframe. She'd been managing it in increments: adjust, wait, check, adjust again.
Warren was watching the circuit breaker panel when he said, "There's something else."
She didn't look away from the attitude indicator. "Tell me."
"The rear equipment panel—the one near row 22. Your passenger went back there, you said."
"60 seconds."
"The avionics cooling duct runs behind that panel. If someone introduced an obstruction—something as simple as a wadded material blocking partial airflow—it would cause a slow thermal buildup in the avionics bay." He paused. "It wouldn't show immediately, but over a two-hour flight at altitude with the system working hard..."
"...it would start to affect the systems it cools," she said. "Autopilot computers, flight management, navigation."
"Yes."
She thought about the micro-variations she'd noticed in the engine sound in act two, the electrical flicker, the altitude fluctuation that the autopilot had overcorrected for. All of it sitting downstream of a thermal issue in the avionics bay that was building quietly, invisibly, degree by degree.
"The circuit breakers confirm intentional electrical interference," she said. "The fuel control restriction confirms fuel system tampering. And now a possible avionics cooling obstruction: three separate system categories." She kept her voice level. "Whoever did this knew the aircraft. They knew which systems were independent enough that each failure would look like a coincidence."
Warren was quiet for a moment. "This wasn't someone who read a manual," he said. "This was someone with maintenance access history."
She nodded slowly. She was beginning to understand the shape of it: not all of it, not yet, but the shape.
"We have a warning," Warren said sharply.