All this poses a serious challenge to the airlines, who have little idea who is causing the severe disruption they have faced almost every day this week.Although so far all threats have turned out to be hoaxes, airlines have no choice but take each threat seriously."They have a triage system, but follow the same protocols for each until they are absolutely sure there is no threat," says Marco Chan, a former commercial airline pilot and aviation expert at Kingston University."That could involve a mid-air inspection, but definitely a search once the plane has landed."Passengers might not even know there is an issue until they are told to disembark. It can cause disruption, but that is a small price to pay when safety is at stake", he adds.The sight of sniffer dogs and specialist teams on the tarmac searching for explosives on commercial planes may cause alarm.So far, the disruption too has been limited to the few thousand passengers who have been directly involved.Paul Mason, an aviation security expert, says there will be a financial cost to the airline involved, but planes get diverted every day."The number can sometimes run to over a hundred planes daily, for things like technical issues, medical emergencies, even the weather," he adds. "They far outweigh the few which have been diverted due to hoaxes.

So airlines are well equipped at dealing with the unexpected."It is also unlikely that customers will be able to get refunds, he explains, because these incidents are not the fault of the airlines.The more worrying aspect over the past few days will be the seeming random nature of the targets and the lack of any credible intelligence regarding who is behind the threats.Aside from emails suggesting that an extremist misogynist group had claimed responsibility for a handful of the incidents - although since denied by its founder - there appear to be few leads.With 20 years of military experience as well, Paul Mason says the incidents bear the hallmarks of hybrid warfare, which involves unconventional methods such as cyber attacks."It does feel co-ordinated," he says. "Russia has said it's got nothing to do with it, but it could be proxies. It's a very easy way to create disruption and chaos, with plausible deniability.""That's the problem.

Someone can have an opinion on who is behind it, but if the perpetrators are using sophisticated technology, it will be very hard to trace them."He does say however that if misguided individuals try to copy the threats they could find themselves in serious trouble.The Aviation Security Act 1982 states that "intentionally communicating false, misleading, or deceptive information that endangers - or is likely to endanger - the safety of an aircraft in flight is a serious criminal offense".The maximum sentence is life imprisonment.There is precious little that airports and airlines can do to guard against actually receiving threats, as they can come from a vast range of sources. But the punishment is designed to act as a deterrent.As Paul Mason warns: "Someone might think it's a laugh and very easy to do, but unless they are very sophisticated, they are highly likely to be traced.

And find themselves facing prison."