The A340 that was lost over the Atlantic was caused by pilot error.
Anybody who has ever flown any aircraft knows that if you get a stall warning, you push forward or at the very least, don't panic and pull back.
Imo, it was a case of modern day aircrew becoming too reliant on electronic toys and too much time in a simulator instead of the real thing.
I recently watched a documentary on the causes of that crash now the black box has been fully analyised.
Firstly the French Captain decided to fly directly into a very severe storm, that other planes that night flew around; a common practice apparently and pure common sense.
The said Captain then left the two co-pilots on board to cope with terrible conditions. One of those was very inexperienced, but he was the one allowed to take command of the aircraft.
At the point were the instruments failed due to the icing up of the sensors, the commanding pilot panicked, as did the other co-pilot, as they could not understand what was happening.
During this panic the aircraft went into a stall due to lack of speed, and the inexperienced pilot kept pushing the stick back without increasing engine speed. The plane continued to fall, at, if I remember correctly 3,000 feet a minute (?)
The aircraft was rapidly descending, and the other co-pilot went to wake the Captain. He arrived on the flight deck and tried to work out what was happening. He did not realise, until it was too late, that the commanding pilot had continued to push the stick back, instead of forward to speed the plane up as well as increasing engine speed.
At their now lower altitude, the outside sensors thawed and started working, but by then it was just too late. The Captain is heard shouting at the inexperienced co-pilot when he realised what he had been doing. There was by now no altitude for corrective action, and the plane ploughed into the sea and went straight down.

French airline pilots have been retrained, as well as all others around the World being reminded about how special procedures must come into effect when "flying by wire" aircraft and if the instruments fail, requiring old fashioned pilot skills and knowledge to overcome.
The Captain exercised a dereliction of duty in his actions that night, but of course died with everyone else as a price.