It is... not yet possible to answer questions which we think are essential before we can make the recommendations which must precede a resumption of flights

Gilles Ricono

After a meeting of crash investigators and aviation experts in Paris, senior ministry official Gilles Ricono said the technical investigation into the crash was going quickly, but not enough was yet known about the causes of the accident to allow new safety measures to be put in place for Air France's five remaining supersonic jets.

The panel of experts - including representatives of Air France and the aviation authorities - are seeking to establish the chain of events that led to the 25 July crash.

Flight AF4590 ploughed into a hotel in the town of Gonesse on the outskirts of Paris, just minutes after taking off from Charles de Gaulle airport.

All 109 people on board the plane were killed, as well as four people on the ground.

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France's Accident Investigation Bureau (BEA) is expecting to release its preliminary report into the crash at the end of August. Ministry officials have said the flight ban could remain in place until then.

The plane crashed into the hotel just minutes after take-off

Officials are reported to favour upgrading checks on tyres before take-off, improved cockpit instrumentation to detect tyre failure, and more frequent runway inspections.

Investigators have already said that they know that one, and possibly two, tyres burst, that there was an intense fire caused by a major fuel leak, and that the flight crew could not retract the landing gear and had problems with two of the four engines.

However the Transport Ministry said it was still not clear what exactly went wrong and in what order.

Deflectors

Investigators confirmed a report in the newspaper USA Today on Thursday which said that part of the plane's undercarriage designed to deflect spray on wet runways had been found on the tarmac after the crash.

BEA's Paul-Louis Arsanian said the deflector issue was just one part of the inquiry

The newspaper said investigators were examining whether the deflector flew off and punctured a fuel tank, sparking the massive fire that trailed from the plane as it took off.

However BEA head Paul-Louis Arsanian appeared to play down the reports.

"I don't know why it is suddenly such a scoop," he said. "It is not THE element of the inquiry. It is one of the elements of the inquiry," he said.

USA Today said the deflector had been implicated in a fuel tank leak in 1993 when the part flew off after a tyre exploded on a British Airways Concorde, puncturing a tank.

The newspaper said that BA had later modified its Concordes to prevent the part from coming loose, but it was unclear from the reports whether Air France had modified its own fleet.

Air France declined to comment.