Air France crash remains a mystery after 6 months

Investigators are still unable to pinpoint why an Air France passenger jet crashed into the Atlantic on June 1, killing all 228 people on board, France's official BEA aviation accident authority said on Thursday.

The BEA said in its latest report into the disaster that speed probes on Air France flight AF 447, which was flying from Rio de Janeiro to Paris, were one factor in a string of events that led to the crash but not the sole cause.

"At this stage, despite the extensive analyses carried out by the BEA on the basis of the available information, it is still not possible to understand the causes and the circumstances of the accident" the report said.

The 'black box' flight recorders are still missing and only small parts of the wreckage have been found of the Airbus A330. However, a string of automated messages just before the crash showed there were problems with data from the speed probes.

"The BEA confirms that the phenomenon of inconsistency in the measurement of airspeeds was one of the elements in a chain of events that led to the accident, though this alone cannot explain it" the BEA said in a report.

Noting that planemaker Airbus had recommended replacing Pitot speed probes on A330 and A340 planes and that airlines including Air France had followed the advice, the BEA issued two additional recommendations.

The first one was to improve the effectiveness of the equipment for localising airplanes and collecting the recorded data for analysis in case of an aviation accident.

The second one was to better characterise the composition of cloud masses at high altitude in which long-range airplanes fly, and to draw conclusions in relation to airplane certification.