Neither knew that a tiny sensor on the left side of the plane, just below Suneja’s window, had a twenty-one-degree misalignment in its delicate innards—an oversight by mechanics who had inspected it. The device, known as an angle-of-attack sensor, was basically a weather vane. It measured the angle of the wing against the oncoming air—too high, and the plane might stall. In the triple-redundant engineering of a product now more than a century old, dating to a pair of bicycle makers who hitched a 12-horsepower engine and a chain sprocket to a spruce wood frame, it wasn’t even considered a
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