The crash of Air France flight 447 from Rio to Paris last year is one of the most mysterious accidents in the history of aviation. After months of investigation, a clear picture has emerged of what went wrong. The reconstruction of the horrific final four minutes reveal continuing safety problems in civil aviation. One tiny technical failure heralded the impending disaster. But the measurement error was so inconspicuous that the pilots in the cockpit of the Airbus A330 probably hardly noticed it. snip . . .