What is behind the US and UK bans on laptops, tablets and other devices in air passengers’ cabin baggage, asks Ian Taylor

The US ban on electronic devices bigger than a smartphone in carry-on baggage came out of the blue, although I’ve long wondered whether a laptop bomb could bring down an aircraft.

Its sudden announcement, without consultation with the International Civil Aviation Organisation (ICAO) or airline association IATA, didn’t help.

In fact, not only could it happen but it has – certainly in the case of the Daallo Airlines’ crash in Somalia in February 2016, possibly in the case of the Egyptair crash in May 2016, and perhaps even in the case of the Russian holiday jet disaster following take-off from Sharm el-Sheikh in October 2015.

It was no surprise when the UK followed the US in imposing a ban, but it is odd other states have yet to follow especially since Britain’s Home Secretary Amber Rudd suggested on TV in late March that the ban could be extended.

Appearing on the BBC and asked why the ban did not apply to all flights, Rudd said: “It’s difficult to say how far this will go, whether we may at some point arrive at that place.”

This is just one of several anomalies. Another is the substantial difference between the US and UK bans.

Why did the US Department of Homeland Security pick on nine carriers at 10 airports, including Gulf giants Emirates, Etihad and Qatar Airways, but exclude US carriers which fly from the same airports?

Why did the UK exclude the Gulf airports and airlines? And why, if a laptop containing a bomb could evade detection at Dubai, Doha or Abu Dhabi, couldn’t it evade detection anywhere?

The UK ban is both less extensive and more consistent than the US restriction, banning devices in carry-on baggage on all flights from six countries, including those by UK airlines. It added two countries excluded from the US ban (Tunisia and Lebanon) from which there are no direct flights to the US.

It is hard not to see the US ban on the Gulf airports and airlines as a riposte to the Gulf carriers’ case against accusations of unfair state aid levelled by US carriers, which lies in President Trump’s pending tray.

Indeed, the Financial Times suggested the ban be interpreted as “a disguised piece of protectionism”, and some of the anomalies seem to confirm this. Yet some of the other restrictions can be explained.

UK transport secretary Chris Grayling insisted the ban did not mean the affected airports are not safe, arguing: “This is not a vote of no confidence in the security measures in any other country.”

Grayling’s defence of “our partners”, and the US Department of Homeland Security’s apparent confidence that US airlines at affected airports would not be compromised, suggests it’s not the security checks and screening that are considered the problem, but the conditions airside – specifically, concern that aircraft could be interfered with while parked.

The bans make no sense otherwise.

In that case, insisting no device bigger than a phone be on board means any laptop pulled out (one planted on the aircraft for a bomber posing as a passenger) would be instantly spotted.

Why allow smaller devices? They leave less room for explosives.

We might ask how much safer a bomb in a laptop in the hold of an aircraft might be than one in the cabin? Well, a laptop in the cabin can be positioned next to the fuselage and a relatively small amount of explosive blow a hole big enough to bring down an aircraft.

A laptop in the hold will be in a bag, among a great many other bags and unlikely to be next to the fuselage. It would also require a timer to set off an explosion which would take up room and mean greater risk of detection.

As a counter to that, security staff can demand a laptop taken through security in cabin baggage be switched on (a routine requirement in the US), meaning it must retain the parts to work, while a device in the hold could be inoperable.

But airport security consultant Jim Termini told the BBC an electronic device could be “turned on [and] you can prove functionality while it is still a valid IED [improvised explosive device]”.

The problem, according to Termini, is that these IEDs “are incredibly difficult to identify with X-ray technology”.

So security consultants appear to agree on the underlying concerns behind the ban even where they disagree on its effectiveness.

One security expert told Travel Weekly: “There is the potential to bring on a lot of different bits of kit – a laptop, a couple of phones, an iPad.

“If you have the technology and you’re clever enough with it you can make something that may have a different capability from a device in isolation.

“If you look at what happened in Afghanistan, at IED threats, every time we find ways to defeat these kind of devices the enemy innovates and comes up with less and less metal content until it’s very difficult to detect. This is a permanent race.”

The airlines appear largely sanguine. Emirates’ president Sir Tim Clark noted: “The airline industry is no stranger to new security protocols. We must expect and adjust to these unexpected situations.”

My guess is that his language, and certainly that of some of his rival CEOs, was rather more colourful in private.

Passengers are prone to become frustrated with airport security as it is. Personally, I prefer a 20-30 minute queue to being blown up at 35,000 feet.