It turns out Air France 447 may have crashed mainly mainly because of pilot error:
Almost as soon as [the flying pilot, 32-year-old Pierre-Cédric] Bonin pulls up into a climb, the plane's computer reacts. A warning chime alerts the cockpit to the fact that they are leaving their programmed altitude. Then the stall warning sounds. This is a synthesized human voice that repeatedly calls out, "Stall!" in English, followed by a loud and intentionally annoying sound called a "cricket." A stall is a potentially dangerous situation that can result from flying too slowly. At a critical speed, a wing suddenly becomes much less effective at generating lift, and a plane can plunge precipitously. All pilots are trained to push the controls forward when they're at risk of a stall so the plane will dive and gain speed.
The Airbus's stall alarm is designed to be impossible to ignore. Yet for the duration of the flight, none of the pilots will mention it, or acknowledge the possibility that the plane has indeed stalled—even though the word "Stall!" will blare through the cockpit 75 times. Throughout, Bonin will keep pulling back on the stick, the exact opposite of what he must do to recover from the stall.
The article includes a good portion of the CVR transcript in both French and English, including the moment seconds before the crash when the plane's captain—who was sitting in the jumpseat and not at the controls—finally realizes what Bonin is doing wrong.
It's a startling example of a pilot forgetting basic flying principles and a crew that fails to manage its own communications.