Metrojet crash in Sinai caused by IS militants?

First the facts. On Saturday morning, Metrojet flight 7K9268 crashed into the Sinai Peninsula. The flight’s planned route was from Sharm el-Sheikh to St. Petersburg, Russia. Click here to see the flight path, altitude and speed changes acquired by Flightradar24. All three of their receivers stopped receiving data at exactly the same time, 0413 GMT.

So what happened? The jetliner -- a leased Airbus A-321 operated by Russian airline Kogalymavia -- apparently disintegrated while at cruising altitude. It either exploded or was blown apart or just... broke up. Within hours, a militant group affiliated to Islamic State in Egypt claimed responsibility for bringing down the jet, but Egypt and Russia disputed the claim, suggesting militants in northern Sinai, where Egypt has been fighting an Islamic insurgency, did not have the weaponry to hit a flight at 31,000 feet. Pictures of the debris show no signs of burn or scorch marks.

The airliner's black boxes have been recovered, but have not yet been analyzed. Yesterday, however, an official of Kogalymavia put the disaster down to "external activity". Alexander Smirnov, the deputy director of the airline, ruled out a technical fault and pilot error. "The only [explanation] for the plane to have been destroyed in mid-air can be specific impact, purely mechanical, physical influence on the aircraft," he said. "There is no such combination of failures of systems which could have led to the plane disintegrating in the air."

A regional expert on Sinai security said on Sunday that the militant group’s statement "said they were responsible for downing the plane, not shooting it down." Zack Gold told the Guardian, "A legitimate ISIS-supporting account in Sinai said, 'Why is everyone talking about shooting it down, why is no one talking about a bomb or suicide bomber on board.'"

He explained that if a bomb had been planted on the plane, it would suggest security systems at Sharm el-Sheikh airport had been infiltrated or compromised, which would raise a whole range of other questions. But, he added, there has been nothing to support the claim so far, such as a pre-mission video of a suicide attacker. "The group does not have a history of major fabrications, but at the same time it's curious that they would make this claim without providing any kind of evidence. They have military capabilities, but to carry out this kind of terrorism [on a plane] they would have to display organization they haven’t shown [before]."

If it turns out that the IS affiliate in Egypt is indeed responsible, what does that portend for the American-led "war on terror" in the Middle East? Will the Russians, now bombing the jihadis in Syria, take the fight to the jihadis in Egypt? And which side will the USA take? Stay tuned.