San Francisco Frontiers - Smoke doesn't reveal what caused EgyptAir crash, experts say

So what can be inferred from this latest discovery?

- What were the signals? -

Shortly before the plane disappeared from the radars, it transmitted a series of automatic messages indicating there was smoke in the cabin, France's BEA aviation safety agency said.

According to specialist magazine Aviation Herald, the Aircraft Communications Addressing and Reporting System (ACARS) messages read: "smoke lavatory smoke" then "avionics smoke" -- referring to the plane's electronic systems. Both messages were confirmed by BEA.

But the agency did not comment on a third message cited by Aviation Herald, which indicated a "fault" with the FCU, the pilots' flight control unit in the cockpit.

- Do they point to a cause? -

A BEA spokesman said it was "far too soon to interpret and understand the cause of Thursday's accident as long as we have not found the wreckage or the flight data recorders."

Jean-Paul Troadec, a former BEA director, agreed: "All you can say... is that there was smoke. The smoke could be due to a fire in the plane following a technical problem, or it could also mean an explosion... but it is far too early to formulate hypotheses."

- Why didn't the pilots raise the alarm? -

"The fact that there was no distress call doesn't necessarily mean anything," Troadec said.

"The pilots maybe had other things to do, reacting to the event. Sending a message is not the first priority."

Francois Grangier, an airline pilot and judicially certified expert on crash investigations, agreed there might not have been time.

"A fire is extremely rapid, extremely violent, and you know when smoke begins to invade a cockpit the first priority is to fight the smoke."

He said the crew would have been wearing oxygen masks and that one of them would have had to read the procedures off a printed checklist if display screens were no longer legible.

"So you can see how calling an (air traffic) controller who can do nothing besides tell you your position" would not be a priority, he said.

- Did the pilots have time to react? -

"Clearly, given the time of the (ACARS) messages and the sequence of the messages, everything happened in a minuscule space of time," Grangier said.

"Basically it means they had a very, very, very rapid invasion of smoke into the cockpit, and visibility can be reduced to a few centimetres when there's smoke. So... it's possible they couldn't see anything at all. And then the temperature could become unbearable."

G.Miller--SFF