A spate of bomb threats against passenger flights has forced diversions, emergency landings and military escorts across European airspace this week, stoking fear among passengers and heaping pressure on airlines.
Authorities have described the more than two dozen threats as malicious hoaxes, and no actual attacks have been carried out. But the incidents have highlighted the huge impact that even false claims can have on a tightly scheduled aviation network.
"This is really quite exceptional, I've never seen this before in my whole career," Wilfried Covent, head of security firm Covent Consulting with a specialization in aviation, told CNBC by phone.
"We've had bomb threats in flights and towards airports, but usually maybe a single copycat, one or two max. What we see now is a systematic attack on airlines and airports."
An email sent to European broadcasters on Friday claimed to be from the leader of the group behind the plane hoaxes and also said bombs had been placed in their buildings, prompting evacuations. No bombs were found at the sites.