Remotely Detonated?

One thing has puzzled me ever since Russian Airbus A321 fell from the sky....

How could ISIS have timed the explosion and spiraling of the Russian jetliner (if, indeed, the video below is authentic)?



Could an explosive device have been remotely detonated by someone who brought aboard a carry-on bag? 

After all, remote detonation by someone aboard would have ensured that an unforeseen flight delay would not have interfered with ISIS's making of the propaganda film, which must have required that the videocam was in place.

The passenger detonating the device in the cargo hold would have been following the flight path on one of those screens showing the exact flight path of the airplane in real time.

Another reason that I've been thinking along these lines: the recent uptick in screening measures of both passengers and carry-on bags.

Russian Jet Crashed Because of "An External Impact On The Plane"

Just as ISIS claimed:

Metrojet officials say something outside the plane flying to St. Petersburg caused it to crash in the Sinai desert and that made the plane's crew incapable of responding. 

Viktor Yung, a director general of Metrojet, says Monday "from the moment since the events took a tragic turn, the crew became incapacitated." 

He says that's why there was not "a single attempt to get in touch (with air traffic control) and report the situation on board." 

Another Metrojet official, Alexander Smirnov, has ruled out technical faults or pilot error as a reason for Saturday's crash, saying Monday it had to be due to "an external impact on the plane."