An airplane's nervous system is its electrical wiring, and on many older aircraft, nerves are a bit raw. The polymer sheaths covering wires are subjected to "everything from deicing salts to Coca-Cola, airborne particles, vibration and rubbing against sharp corners," says Northwestern University materials scientist Thomas Mason. Cracks, holes and thin spots in the sheaths can cause breakdowns or disaster: Investigators suspect a faulty fuel-gauge wire caused the 1996 explosion of TWA Flight 800.

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