Airlines across Europe received a series of bomb threats on Thursday morning for the second time this week, forcing many to make unplanned or escorted landings, although none of the threats immediately proved to be genuine.

While no country has attributed blame for the threats, they come at a time when European officials have been blaming both Russia and Iran for what they describe as “hybrid attacks”. Moscow and Tehran both deny any such campaign.

Aer Lingus flight EI402 from Dublin to Rome landed safely on Thursday at Evreux airport, 100 km (62 miles) west of Paris, after being diverted as a security precaution, the Irish airline said in a statement.

Bulgarian officials reported three aircraft making emergency landings in the Balkan country because of bomb threats.

Airplanes flying from Copenhagen and Madrid landed safely in Sofia, the interior minister said, according to broadcaster bTV.

A third aircraft, from London, was diverted and landed in Plovdiv, Bulgaria’s second-largest city, local media said. The government did not respond to requests for comment.

Czech, Italian, Polish authorities also report bomb threats

Czech police said on X that four airplanes heading to Prague had received bomb threats on Thursday and that authorities were making preparations for the landings, although they assessed the credibility of the threats as low.

Italy’s air force safely escorted a Finnair plane from Helsinki to its scheduled landing in Rome, a person close to the matter said. Another Finnair flight from Helsinki, operated by Jettime, landed as normal in Vienna after receiving a bomb threat, the Finnish carrier said.

Polish airline LOT said a flight from Warsaw to Brussels had landed safely at its destination after a security warning, and no suspicious items were found.

It also said a LOT flight to Paris had been stopped as it was taxiing towards take-off and that its passengers had then been transferred to another aircraft as a precaution.

Italian media reported that a Wizz Air flight from Milan to Warsaw had to land in Vienna due to a bomb threat.

On Tuesday, at least seven flights and a cruise ship received bomb threats, causing disruption at airports across Europe, although no devices were discovered.

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 cheap, deniable disruption efforts.

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,” Almog said.

“Different essential services are experiencing disruption that carries economic costs and can undermine public confidence.”