The Bureau d’Enquêtes et d’Analyses pour la Sécurité de l’Aviation civile (BEA) has released a report on the incident with an Air France Airbus A340-313 on 22 July 2011 over the North Atlantic Ocean. The Airbus took off from Caracas-Maiquetía Simón Bolívar airport bound for Paris Charles de Gaulle.
One hour into the flight, at FL350, the aircraft entered a zone of moderate turbulence. Following an airspeed and Master warning, the aircraft started a climb with a rate of 1,950 ft/min which increased 20s later to 5,700 ft/min. The crew were not aware of the airplane gaining altitude. Instead they noticed that the airspeed was decreasing which eventually led to the crew selecting the TO/GA mode and N1 at 100%.
One minute and seventeen seconds after the aircraft had begin its ascend from FL350, it had reached FL380. At this point the pilots surprisingly noticed that the altitude was 38,000 ft. They corrected and the aircraft descended back to FL350.
The flight continued without further incident to Paris-Charles de Gaulle airport, where the crew landed at 8 h 33.
Read the full report: F-GLZU 22 July 2011 (Acrobat Reader required)