Fears hoax calls will be used to wreak more havoc
As police and intelligence officials remain on peak alert in the wake of Friday night's terror attacks in Paris, fears have emerged that Isil supporters could try to wreak extra havoc by flooding emergency services with fake calls.
The warnings came after two Air France jets bound for Paris from the US were diverted on Tuesday evening because of anonymous threats received after they had taken off. US officials later found no evidence of bombs on board.
Meanwhile, German police found a fake bomb on a train in the city of Hanover on Tuesday night, where a Germany-Holland friendly was cancelled because of a separate earlier threat passed on to them by an intelligence source.
The hoax calls follow a flurry of similar threats made against US and Canadian airlines earlier this year.
In January, a fortnight after the 'Charlie Hebdo' terror attacks in Paris, US fighter jets were scrambled to escort two Delta Airline flights when bomb threats were made against them.
And during the summer, four airliners with the Canadian firm WestJet were forced to make emergency landings after the airline received warnings that targeted specific flights.
Matthew Finn, managing director of the London-based aviation security firm Augmentiq, said that such incidents had "an incredible operational and economic impact" and that it was possible that Isil followers in Europe could adopt it as a tactic.
"This might be something they would try, given the low tolerance that the French have for security scares at the moment," he said.
"Hoaxers know that people are very sensitive at the moment and that any hoax call can cause disruption."
Hoax bomb calls and emails are usually the work of a wide range of people, with those purporting to be terrorists often turning out to be individuals with psychiatric problems or purely criminal intent.
Mr Finn said that airlines and public bodies had no choice but to take the threats seriously, although they had means of grading them according to degree of urgency.
"This can cause havoc at airports - not only do you get a flight delayed, you may have the airport shut for a while, passengers having to be re-screened, staff asked to work extra hours and people missing connections," he said.
"Even a small window can have a huge impact."