By Hugh Schofield
BBC News, Paris
The disappearance of Air France 447 is shrouded in an air of mystery that sets it apart from other aircraft disasters.
Nearly all air crashes take place at or near airports - during take-off or landing. But the Airbus 330 came down four hours out of Rio de Janeiro, somewhere in a vast area of the Atlantic Ocean.
There was no distress signal.
The first Air France officials knew of something being wrong was when the plane failed to turn up on radar in Senegal.
For many hours it was possible to think that AF447 had had a communications failure, or that it had made a forced landing at sea, or even that it had been hijacked.
For a time the arrivals board at Charles de Gaulle airport bore the word "delayed" - as if to keep alive as long as possible the dwindling hope of a miracle.
The suffering of family members having to face the appalling reality can only be imagined.
But it must have been made worse by the absence of any clear information about what has happened. Until wreckage is found, no-one is officially dead.
The flight was initially listed as delayed on arrivals boards
In the absence of news, the airwaves have been crammed with all the regular disaster coverage: the coy intrusiveness of the television cameras, the repeated interviews with experts, the desperate hunt for a new angle - like the miracle couple who missed the plane because of a late taxi - in order to vary the fodder.
Consensus quickly developed that the most likely cause of the accident was a lightning strike.
But as more than one expert pointed out, if lightning alone caused planes to crash, then few people would be so foolhardy as to risk flying.
"For a plane to get hit by lightning is totally routine," said Pierre Sparaco, a member of the French Air and Space Academy.
"That is not enough to explain it. There must be a missing link. It is clearly something and something.
"Accident investigators talk always of a 'sequence of catastrophic events', and sequence is the key word," he said.
"It is not this thing or that thing that went wrong. It is this thing going wrong, leading to that thing going wrong etc etc."
According to Mr Sparaco, even in a worst case scenario, with lightning wiping out all the electronics, a modern airliner is still flyable.
"Something kicks in called the RAM air system, in which a small propeller descends and because of the speed of the plane generates enough electricity to run vital instruments.
"So even if there is a total power failure the pilot can still fly by wire long enough to get to land."
Meteorologists have been called in to explain what else might have happened, the extra factor that might have come on top of the lightning.
The accident took place in a turbulent area along the equator known as the Intertropical Convergence zone.
The zone has long been feared by sailors and aviators. In French, it is called the "pot au noir", meaning the murky cauldron.
According to meteorologist Pierre Lasnais, the zone "is prone to storms and lightning, but also to mini-cyclonic phenomena, which create extremely strong up currents, as well as hail stones that can be bigger than tennis-balls".
"It's possible for a plane to be exposed to lightning, and at the same to be caught in an up current which can reach speeds of 200 km/h," he says.
"You can imagine the effect that has on a plane - complete depressurisation of course, almost uncontrollable," he said.
But all this is the purest speculation.
Because until they find it, no-one can talk with any authority about what really happened to Flight 447.