LOS ANGELES AND PARIS — The first sign of trouble was a glitch that appeared in the air speed sensors.
Inside the sleek cockpit of Air France Flight 447, according to aviation experts, the crew would within minutes be confronted with a cascade of mysterious system failures.
The atmosphere of a routine international flight would vanish. Warning lights would be flashing and alarms would sound as one high-technology system after another of the highly automated jetliner began going off line.
At the same time, the Airbus A-330 was flying through turbulence caused by a tropical storm rising from the equator 35,000 feet below that was capable of jostling the pilots so strongly that they may have had difficulty reading the cockpit instruments.
Were the wings level? What speed were they traveling? Why were the computers reducing their ability to move the plane's control surfaces? As the pilots frantically worked to understand what was happening during the chaotic final minutes before the plane crashed into the Atlantic Ocean on May 31, the sky was illuminated by sporadic flashes of lightning.
"It would tax a really experienced pilot," said Robert Ditchey, a pilot, aeronautical engineer and former U.S. airline executive. "All hell is breaking loose."
French authorities investigating the accident that claimed the lives of 216 passengers and 12 crew members are still at the early stages of determining the cause. But preliminary evidence has already made it clear that the flight crew was battling a multitude of problems during the final four minutes.
The jetliner sent out 24 automated messages about abnormalities to Air France's maintenance department in the minutes before the crash. The airline has not released that data, but some information has been leaked to outside aviation experts, and ultimately to the news media.
The initial event, based on what is known so far, was the simultaneous failure of three sensors that determine airspeed. The sensors are called pitot tubes, a decades-old technology that pilots still depend upon.
Pilots rely on several instruments for speed information. A system of laser gyroscopes and a separate GPS system can tell pilots their ground speed. But the pitot system provides data about the speed of air flowing across the wings, crucial to maintaining lift.
If all that information disappears, as apparently happened, Air France provided pilots with an emergency procedure checklist.
