Berlin: A wave of mysterious drone flights over European Union and NATO member states in recent weeks has triggered widespread alarm among the public and officials, with some incidents blamed on Russia and described as an unprecedented challenge to Europe’s airspace security.

The unexplained incursions, which intensified last month, have led to heightened tensions and fresh questions about NATO’s preparedness to counter aerial threats from Moscow. Several European officials suggested the overflights might be an attempt by Russia to test the alliance’s response mechanisms.

On September 10, a swarm of Russian drones reportedly entered Poland’s airspace, prompting NATO aircraft to scramble and intercept, shooting down some of the devices — marking the first direct encounter between NATO and Russia since Moscow launched its full-scale invasion of Ukraine on February 24, 2022.

Just days later, NATO jets were dispatched again to escort three Russian warplanes out of Estonia’s airspace.

Since then, suspicious drone flyovers have been reported near airports, military installations, and critical infrastructure across Europe. The incidents have prompted EU defence ministers to agree on creating a “drone wall” along their borders — a coordinated effort to detect, track, and intercept drones violating European airspace.

While Russia has been blamed for several of these incidents, the Kremlin has denied any deliberate involvement. European authorities, meanwhile, have released limited details about the intrusions, and in some cases acknowledged them only days after they occurred.

At times, officials were unable to verify reported sightings. In Denmark, authorities received more than 500 reports of drone sightings within a 24-hour period — many of which later turned out to be misidentified stars or lights in the night sky.

Governments are now debating how to respond in real time, including whether to grant permission to shoot down unauthorised drones.

The latest breach occurred on Thursday, when Russian military aircraft briefly entered Lithuania’s airspace — a move Lithuanian President Gitanas Nausėda condemned as a “blatant breach of the territorial integrity” of his NATO and EU member nation.

Airport disruptions across Europe

Germany’s Munich Airport was forced to close twice earlier this month following drone sightings, while in Denmark, drones flying over Copenhagen Airport on September 22 caused major air traffic disruptions at Scandinavia’s largest hub.

Danish Prime Minister Mette Frederiksen said Russian involvement could not be ruled out, calling it “the most serious attack on Danish critical infrastructure to date.”

On the same evening, a drone sighting was also reported at Norway’s Oslo Airport, forcing air traffic onto a single runway. Authorities are investigating whether the two incidents were connected.

Danish military sites targeted

Between September 24 and 25, drones were also spotted over four smaller Danish airports — two of which double as military bases. Danish Defence Minister Troels Lund Poulsen said a “professional actor” was likely behind the “systematic flights.”

During the same period, Danish media reported sightings near Karup Air Base, Denmark’s largest military installation. The Defence Ministry, however, declined to confirm the reports, citing “operational security and the ongoing investigation.”

“For reasons of operational security and the ongoing investigation, the Defence Command Denmark does not wish to elaborate further on drone sightings,” the ministry said in a statement.

Drone activity over German infrastructure

The authorities in northern Germany are also investigating reports that drones were used to spy on critical infrastructure in the state of Schleswig-Holstein.

On September 25, multiple drones were seen above a power plant in Kiel, near a university hospital and a shipyard, according to Der Spiegel.

Regional Interior Minister Sabine Sütterlin-Waack told lawmakers that flying objects of “various types and sizes” had been observed. Chief Public Prosecutor Stephanie Gropp confirmed that an investigation was underway.

Der Spiegel reported that two small drones had been seen over the Kiel factory premises of TKMS, a maritime defence technology company. Later, a “combined drone formation” was reportedly observed above the university hospital and power plant, with further sightings over government buildings and the Heide oil refinery.

Additional drones were also spotted over a military base in Sanitz, in the neighbouring state of Mecklenburg-Western Pomerania, the weekly said.

Russian aircraft in Baltic airspace

Last month, Estonia summoned a Russian diplomat after three Russian fighter jets entered its airspace without permission and remained for about 12 minutes.

Weeks later, the Lithuanian Armed Forces said that around 6 p.m. local time on Thursday, two Russian aircraft — a SU-30 fighter jet and an IL-78 refuelling aircraft — violated Lithuanian airspace, flying roughly 700 metres (765 yards) inside before departing after 18 seconds.

Officials believe the planes were likely conducting refuelling exercises near Russia’s Kaliningrad exclave. Two Spanish fighter jets on NATO air policing duty were scrambled in response.

The Russian Defence Ministry, however, rejected the Lithuanian account, insisting that Su-30 jets were conducting “training flights over Kaliningrad in strict compliance with the rules.” AFP