PARIS // Air France Flight 447 was brought down by a "convergence of different causes," although its too early to know what they are, the head of Airbus' parent company said. Airbus made the A330-200 plane flown by Air France that crashed May 31 with 228 people on board en route to Paris from Rio de Janeiro. Industry experts have called the plane one of the safest in the world. "In such an accident, there is not one cause," Eads Ceo Louis Gallois said. "It's the convergence of different causes creating such an accident." Investigators have focused on the possibility that external speed monitors, called Pitot tubes, iced over and gave false speed readings to the plane's computers as it ran into a turbulent thunderstorm. Air France ordered these Pitot tubes, which are made by France's Thales Group, replaced on long-range Airbus planes on April 27 after pilots noted a loss of airspeed data in a few flights on Airbus A330 and A340 models. Pitot tubes on the jet that crashed had not been replaced yet. But Mr Gallois said investigators "don't know if Pitots are part of the accident." "We know that Thales has improved its Pitots with a new one because they had some problems with water at the takeoff and landing," he said. "It was not a problem which is the same as the problem faced by an airplane flying at 25,000 feet." Airbus, and not Thales, is "responsible for the airplanes, that's clear," he said. The Airbus Ceo Tom Enders said the planemaker was working with Air France and the French authority leading the investigation, the BEA, to solve "the riddle about this accident." "It certainly does not provide any consolation to the families and friends of the victims if we look at the statistics that flying today is much safer than 10 or 15 years ago or we look at the A330 group this is one of the safest and most efficient aircraft that ever went into commercial service," Mr Enders said. Finding the plane's flight recorders - whose locater signals begin to fade after 30 days - is key to determining how and why the Airbus A330 went down en route to Paris from Rio de Janeiro. Debris and bodies from the jet also contain crucial clues. "It's essential for everybody to know what happened and we know that it's not easy, Mr Gallois said. "I hope we will find the black box." So far, there is no evidence of an explosion or terrorist act, but there were a number of clues that describe systemic failures on the plane. A burst of 24 automatic messages sent during the plane's final minutes of flight show the autopilot was not on, but it was not clear if it was switched off by the pilots or if it had stopped working due to conflicting airspeed readings. Gallois and Enders spoke on Saturday at a media day hosted by European Aeronautics Defense and Space Co. ahead of the Paris air show, which starts Monday.