“In this particular case yesterday it looks highly unlikely that this was consistent with some sort of explosive device.
“One is inclined to go towards the theory that there had been some interference on the aircraft and on the flight deck or with the control of the aircraft.”
Capt Vivian, who also previously worked as a security adviser to Virgin Atlantic, also expressed surprise that there may have been three security officers – flight marshals – on board the plane though he said this may have been because of the levels of anxiety over the terror threat particularly in Egypt and France.
Another possibility is of a rogue pilot deliberately crashing the plane which may also explain why there was no distress signal.
However, if terrorism is proved and a bomb was smuggled on board the focus for security officials will centre on a possible breach of security at Paris’ Charles de Gaulle airport.
Security was already tight, and under review, after last November’s attacks by jihadist militants in the French capital and since then, some airport staff have had security clearance revoked over fears of links to Islamic extremists.
The flight was the aircraft’s fifth of the day, having also flown to the Eritrean capital of Asmara, the Tunisian capital Tunis and Brussels in Belgium.
Richard Osman, 40, was the sole Briton on board and was said to have been “deliriously happy” after the birth of his second daughter.
A geologist from Carmarthern, Wales, he had been travelling to work in Egypt as part of his job with a gold mining company. His younger brother Alastair described him as a workaholic and a very admirable person who “never deviated from the straight path”.
Egyptian and Greek ships and planes were joined in the search today by vessels and aircraft from the US, Britain and France.
A Ministry of Defence spokeswoman said the Royal Fleet Auxiliary landing ship Lyme Bay and an RAF C130 Hercules aircraft had joined the search efforts.
Some funerals of the missing were due to take place in Egypt with empty coffins – a practice which takes place when the family believe it is unlikely that a body will be found.
Civil aviation minister Sherif Fathi said the disaster was still being investigated but the possibility it was a terror attack “is higher than the possibility of having a technical failure”.
Alexander Bortnikov, chief of Russia’s top domestic security agency, said: “In all likelihood it was a terror attack.”
