Problematic speed sensors on the Airbus A330-200 jet that have been the focus of intense speculation since the crash may have misled the plane's pilots but were not a direct cause, Bouillard said, while admitting that investigators are still a long way from knowing what did precipitate the disaster.
"The investigation is a big puzzle," said Bouillard, who is leading the probe for the French accident agency BEA. "Today we only have a few pieces of the puzzle which prevents us from even distinguishing the photo of the puzzle."
The plane was flying from Rio de Janeiro to Paris when it went down in a remote area of the Atlantic, 930 miles (1,500 kilometers) off Brazil's mainland and far from radar coverage.
The BEA released its first preliminary findings on the crash Thursday, calling it one of history's most challenging plane crash investigations. Yet the probe, which has operated without access to the plane's flight data and voice recorders, appears so far to have unveiled little about what really caused the accident.
The speed sensors, called Pitot tubes, are "a factor but not the only one," Bouillard said. "It is an element but not the cause," Bouillard told a news conference in Le Bourget outside Paris.
Other elements that came under scrutiny in the immediate aftermath of the crash, such as the possibility that heavy storms or lightning may have brought down the jet, were also downplayed in the BEA's presentation.
Meteorological data show the presence of storm clouds in the area the jet would have flown through, but nothing out of the ordinary for the equatorial region in June, Bouillard said, eliminating the theory that the plane could have encountered a storm of unprecedented power. Other flights through the area shortly after Flight 447 disappeared didn't report unusual weather, Bouillard said.
"Between the surface of the water and 35,000 feet, we don't know what happened," Bouillard acknowledged. "In the absence of the flight recorders, it is extremely difficult to draw conclusions."
Representatives of families of the victims said they learned little new and vowed to continue to push for more information.
Charles-Henri Tardivat, lawyer representing victims' families said now that the phase of grief had passed, he expected families to be "even more motivated in trying to get answers and there's going to be significant pressure put on the authorities to continue feeding the facts and the answers that are necessary in this case.
" A burst of automated messages emitted by the plane before it fell gave rescuers only a vague location to begin their search, which has failed to locate the plane's black boxes in the vast ocean expanse.
The chances of finding the flight recorders are falling daily as the signals they emit fade. Without them, the full causes of the tragic accident may never be known.
One of the automatic messages indicates the plane was receiving incorrect speed information from the external monitoring instruments, which could destabilize its control systems. Experts have suggested those external instruments might have iced over.
The Pitots have not been "excluded from the chain that led to the accident," Bouillard said.
Analysis of the 600-odd pieces of the jet that have been recovered indicate the plane "was not destroyed in flight" and appeared to have hit the water intact and "belly first," gathering speed as it dropped thousands of feet, he said.
He also said investigators have found "neither traces of fire nor traces of explosives."
Shortly after the crash, aviation experts indicated that fractures revealed during autopsies of the victims along with the large pieces of wreckage pulled from the Atlantic strongly suggested the plane broke up in the air. There was no immediate explanation for the apparent contradiction between the BEA's findings and those viewpoints.
Bouillard said air traffic controllers in Dakar, Senegal had never officially taken control of Flight 447 after its last radio contact with Brazilian flight controllers at 1:35 a.m., and it wasn't until up to seven hours later that flight controllers in Madrid and Brest, France, raised an alarm. He said the delay was being investigated but was not a cause of the crash.
Brazilian Air Force Col. Henry Munhoz said all required information on the plane's flight plan was passed to Senegalese air controllers.
Some members of the crash victims' families said that without a clear cause to blame the accident on, the interim report held little significance.
Marco Tulio Moreno Marques, a 43-year-old lawyer in Rio de Janeiro, lost both his parents in the crash. He did not bother watching the French investigators' public presentation, saying that without the black boxes, he was skeptical of any findings.
"I think it is difficult that they will ever find out what happened," he said. "They can say a flying saucer hit the plane, but if they don't find the black boxes we will never know for certain what happened."
Kieran Daly, editor of Air Transport Intelligence, said although investigators seem to know very little about what happened due to "a horrendous lack of evidence," it is significant that the plane landed the right way up.
"It suggests they were in some kind of flight attitude," he said.
But he warned that "without finding the black boxes it's going to be phenomenally difficult, maybe impossible, to determine what happened."
Bouillard said life vests found among the wreckage were not inflated, suggesting passengers were not prepared for a crash landing in the water. The pilots apparently also did not send any mayday calls.
He said there was "no information" suggesting a need to ground the world's fleet of more than 600 A330 planes as a result of the crash.
"As far as I'm concerned there's no problem flying these aircraft," he said.
Air France said all elements of the investigation "will be fully and immediately taken into account by the airline" and that it is continuing to cooperate with the investigators with "a commitment to total transparency with regard to the investigators, its passengers and the general public."
The black boxes - which are in reality bright orange - are resting somewhere on an underwater mountain range filled with crevasses and rough, uneven terrain. Bouillard said the search for them has been extended by 10 days through July 10, while his investigation would run through Aug. 15.
Bouillard said French investigators have yet to receive any information from Brazilian authorities about the results of the autopsies on the 51 bodies recovered from the site.
But a spokesman for the Public Safety Department in Brazil's Pernambuco state - in charge of the autopsies - denied that.
"French medical examiners are working together with Brazilian medical examiners and they have full access to all the information obtained from autopsies," the spokesman said on condition of anonymity according to department rules.
Families of the victims met with officials from BEA, Air France and the French transport ministry before the report was released. An association of families addressed a letter to the CEO of Air France, Pierre-Henri Gourgeon, demanding answers to several questions about the plane.
Investigators should have an easier time recovering debris and black boxes in the crash of a Yemeni Airbus 310 with 153 people on board that went down Tuesday just nine miles (14.5 kilometers) north of the Indian Ocean island-nation of Comoros.
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