Bombs reveal major flaws in screening of international freight

Security experts said last night that the Yemeni bombing plot had taken advantage of known weaknesses in the way international cargo is screened.

"There is no international standard for how screening and security checks are done," said Professor David Menachof, expert in supply chain security at Hull University Business School. And there is not 100 per cent screening on air cargo, he added.

But he warned that a knee-jerk response to screen everything will not deal with the threat posed by terrorists using cargo planes to transport bombs. "Scanning the cargo by itself is not the answer. What you've really got to do is a risk assessment, an intelligence-led screening process. Scanning is only one step in that."

Only 3 to 4 per cent of cargo on passenger aeroplanes was being screened worldwide in 2008, Professor Menachof claimed. "Seemingly we've clamped down first on the passenger side of things, and it was almost inevitable that they would go now to air cargo," he said.

The attack also exposed a flaw in our ability to detect suspect devices. The bomb at East Midlands airport was missed initially, despite searches of the cargo that it was hidden in, claimed Chris Yates, an aviation security consultant. "The security cordon at East Midlands was about to be pulled down when they got a call from the Dubai authorities that informed our people how to identify the explosives. By 4pm on Friday they knew they had a bomb."

Britain and other countries remain vulnerable to terrorists switching their focus to cargo planes, he said. "It is a widely held belief within the aviation sector that freight is the weak link in the aviation security regime. This case shows how, despite all of the supposedly high-level security regimes in place around freight, an explosive device can still be got on board a plane."

Vast amounts of freight are flown around the world each day, but just a small amount of pentaerythritol tetranitrate, better know as PETN, used in this weekend's bombing attempts, could wreak havoc if detonated on board a plane.

The substance is one of the most powerful plastic explosives and has become one of the preferred weapons for terrorist groups, mainly due to its stability when handling. As a key component of Semtex, PETN is primarily used to boost military devices such as landmines and is found in detonating cords used for industrial explosions. Only 100g of the chemical is enough to obliterate a car. It is virtually odourless and difficult for airport security to detect.

PETN was used in an attempted assassination of a Saudi security chief in 2009. It is believed that the device used by the suicide bomber was triggered by a phone call from Yemen. The device had similarities with the one found on Friday.