Several flights across Europe have been disrupted by bomb threats for the second time this week.
Around 10 flights have been affected on Thursday, with some diverted.
On Tuesday, at least seven flights and a cruise ship received bomb threats, causing disruption at airports across Europe, although no devices were discovered.
While no country has attributed culpability for the threats, they come at a time when European officials have been blaming Russia and Iran for what they describe as “hybrid attacks” and acts of sabotage. Moscow and Tehran deny any such campaign.
This week, unidentified hackers shut down fridges in supermarkets in several European countries. Some experts said hoax bomb threats could be part of a similar pattern of low-cost, deniable disruption efforts.
On Thursday, Bulgarian officials reported three aircraft making emergency landings because of bomb threats. Planes flying from Copenhagen and Madrid landed in Sofia, the Interior Minister Ivan Demerdzhiev said, according to broadcaster bTV. A third aircraft, from London, landed in Plovdiv, media reported.
Four planes heading to Prague received bomb threats and police were preparing for their landing, Czech police said on X, adding they assessed the credibility of the threats as low. “Nevertheless, we are not underestimating the threat, which is why all necessary security measures have been activated with minimal impact on passengers and airport operations,” police said. “After landing, all aircraft will undergo pyrotechnic inspections.”
Aer Lingus flight EI402 from Dublin to Rome landed safely at Evreux airport, 100km west of Paris, after being diverted as a security precaution, the Irish airline said.
Belgian media reported an airliner forced to land at Brussels' Zaventem airport belonged to the Polish airline LOT.
A Finnair flight from Helsinki, operated by Jettime, landed as normal in Vienna after receiving a bomb threat, a spokesman for the Finnish carrier said.
Finnair earlier said another flight, to Rome, had landed after receiving a bomb threat.
LOT said a flight from Warsaw to Brussels landed safely at its destination after a security warning and no threat was confirmed.
“Following receipt of information regarding a potential security threat to flight LO235 from Warsaw to Brussels, the flight crew was notified of the situation and conducted an on-board inspection in accordance with established procedures. No suspicious items were found,” a LOT spokesman said.
The aircraft landed at Brussels airport, where security services carried out an additional inspection of the plane, which revealed no dangerous or suspicious items.
Eliran Almog, CEO of aviation cybersecurity firm Cyviation, said the repeated threats could serve both to disrupt operations and to observe how airlines, airports and national authorities respond.
"These aviation threats are also occurring in the same period as cyberattacks on supermarket refrigeration systems across Europe," Mr Almog said.
"Different essential services are experiencing disruption that carries economic costs and can undermine public confidence."
