Based on initial physical evidence and information from automatic maintenance messages sent by the aircraft, these people said, the plane bucked through heavy turbulence created by a thunderstorm without the full protection of its flight-control systems -- safeguards that experts say pilots now often take for granted.
Relying on backup instruments, the Air France pilots apparently struggled to restart flight-management computers even as their plane may have begun breaking up from excessive speed, according to theories developed by investigators.
An international team of experts is building a scenario in which it believes a cascade of system failures, seemingly beginning with malfunctioning airspeed sensors, rapidly progressed to what appeared to be sweeping computer outages, according to people familiar with the probe. The Airbus A330, en route from Rio de Janeiro to Paris, crashed into the Atlantic Ocean during a storm 26 days ago, killing all 228 aboard.
