It is now clear that Western security experts view the ability of terrorists to weaponize laptops as the most serious threat to aviation since 9/11. As The Daily Beast first reported last week, the Department of Homeland Security is considering banning proscribe laptops in all cabins on U.S.-bound flights from Europe due to the threat.

Commercial aviation has always been the No. 1 target of terrorists. The successful downing of an aircraft creates an economic consequence that lasts far beyond the horror of the eventit took the airline industry years to recover from the 2001 assaults and cost billions of dollars to wholly change airport security.

Various attempts to repeat that success have so far faileda shoe converted to a bomb, underpants disguising explosives, and, on a shipment flight, a printer cartridge that simply at the last minute was found to contain an explosive device. The defenses against such attempts have now apparently forced the bomb manufacturers to miniaturize the explosive charge to a stage where it can be disguised inside the battery compartments used in larger personal electronic devices, such as tablets and laptops.

And now the revelation that the Oval Office conversation between President Trump and top Russian officials included details of intelligence warns about laptop bombs would explain “what its like” been driving DHSs urgent efforts to persuade European officials the devices should be banned from the cabins of all European flights to North America.

It is also very likely that the intelligence behind this move was so sensitive that U.S. officials did not wish to disclose it during the conference call they held with European Commission officials Friday. Ironically, the two sides are now due to meet in Brussels amid a firestorm of alarm about the exposure by the president of information that could help the Russians and others to trace the source of the intelligence and thereby imperil international collaboration in the fight against terrorism.

As one former, top European intelligence official told The Daily Beast: The U.K intelligence community was already highly angry over Trumps assertion that GCHQ[ Britains equivalent of the National Security Agency] helped Obama wiretap the Trump campaign. This is not conducive to healthy intelligence-sharing relationships. The U.S. intelligence and diplomatic communities are going to be cleaning up after this gaffe for a long time.

From the beginning with Richard Reid, the attempted shoe bomber in 2001, the new generation of bomb producers understood that they did not need a large suitcase device like the one that brought down Pan Am Flight 103 over Scotland in 1988, which would never get through todays baggage screening technology. Instead, they targeted the airplanes most vulnerable component: the skin of the fuselage.

In effect, they were planning a two-stage bomb in which they had to provide merely the first stage, an detonation merely large enough to rend a pit in the fuselage. The aircraft itself then became the devastating second stage. A bomb that rent open the pressurized cabin at cruise altitude of 35,000 feet would trigger an explosive decompression. That would lead to an nearly instantaneous structural breakupand, in some circumstances even to a third detonation when the fuel tanks ignited.

So the bomb manufacturers were always looking to combine as small service charges as would be effective: with a suicide bomber placed in a window seat, where the blast would be most likely to blow a cavity in the airplanes skinideally from a seat over the wings, which happens also to be above the main ga tank.

That is why the new importance about the threat posed by laptop bombs can be traced back to February 2016, when an Airbus A3 20 had a hole blown in its fuselage in precisely that style 15 minutes after it took off from Mogadishu, Somalia. Luckily, the airplane was only at 14,000 feet, and although the cabin rapidly depressurized the pilot was able to return safely.

The only casualty was the bomber himself. Passengers reported that he was blown out of the airplane with bomb.

A former senior British army security expert who reviewed this bombing told The Daily Beast, The bomb was likely placed against the airframe before being explosion. The sum of explosive that can be hidden inside a laptop battery may not be effective if it was detonated elsewhere in the aircraft .( The flight was only half full, so there would have been many window seats available .)

This expert also pointed out that if a laptop bomb is placed in luggage that goes into the cargo hold, it would also be less effective: It would be among other luggage, which would assimilate some of the explosive energy, and would not be sufficient to rupture the bulkhead and cause a destructive depressurization.

Nonetheless any detonation anywhere on an airplane is a big danger, and if the nearby luggage contains other laptops with lithium-ion batteries, it might well be the beginning of a flame that would lead to the demolition of the airplane.

Chris Abbott, executive director of Open Briefing, a British think tank specializing in these new technologies of terrorism, told The Daily Beast that in the case of bombs like the one used on in the cabin of the Mogadishu flight, the bomber himself would have to add at the last minute a non-metallic detonator like a powder to trigger the explosion, which would be impossible in bomb placed in the cargo hold.

Creating a timed or remote non-metallic detonator that is small enough to fit in a laptop and innocent enough to sidestep seeing seems to be the challenge.

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