Russia likely used shadow ships to that repeatedly disrupted civilian aviation, as it monitored military sites and tested the air defenses of NATO nations, according to a report published Thursday by the International Institute of Strategic Studies think tank.
The report, which was shared before publication with The Associated Press, plotted 144 suspected drone sightings across Europe, including in NATO members Germany, France, Belgium, the Netherlands, the U.K., and Denmark, between 2024 and 2026.
Those sightings peaked in late 2025, forcing the temporary closure of several European airports, including in , and .
Danish Prime Minister Mette Frederiksen described the incidents in her country as the 鈥� on Danish critical infrastructure to date.鈥�
The IISS said the Russian campaign was designed to fall below the threshold of triggering discussions for a collective NATO response and was a 鈥渟trategic failure鈥� for Europe that exposed how the continent鈥檚 air defenses are not fit to deal with the current threat.
Air Chief Marshal John Stringer, NATO’s deputy supreme allied commander in Europe, told AP that it is up to each alliance member to decide how to respond to such threats 鈥� and many countries are taking them increasingly seriously.
Several senior European officials said it鈥檚 difficult to attribute the drone incursions to Russia, and Stringer did not blame Moscow. But he suggested the activity fits the pattern of behavior seen in a across Europe that Western officials have blamed on Russia since its invasion of Ukraine in 2022.
Of the handful of countries that have confirmed drone sightings, only Sweden has blamed Moscow directly 鈥� when from a Russian spy ship.
President Vladimir Putin said in May that Russia against Europe.
European nations struggled to respond to drones, the IISS said
Drones are challenging to detect because they fly low and slow, and on radar can look like birds or planes. They can be launched inside, or near, national borders, , which are designed to detect supersonic missiles fired from abroad. And even if a drone is shot down, it鈥檚 extremely difficult to identify where it came from or who sent it and why.
The incursions showed drone defenses in Europe need to rapidly be improved, the IISS said.
Creating a comprehensive picture of threats is often difficult because the responsibility for tackling drones is often split among various authorities, Lt. Gen. Jonny Lindfors, Sweden鈥檚 military representative to NATO, told AP. It鈥檚 also a 鈥渢ough decision,鈥� he said, to decide to shoot a drone down because it could cause civilian casualties.
In a June report, Denmark鈥檚 Defense Command said the armed forces 鈥渃ould have been in a stronger position鈥� to respond to drone sightings and that there were shortcomings in equipment used to detect them. Following the incidents, Denmark and several other European countries said they would boost their drone defenses.
Countries that may have had a 鈥渂enign鈥� view of the danger a few years ago have now realized that counterdrone systems are a critical part of air defense, said Stringer.
Russia is launching drones from shadow ships, the IISS said
The IISS plotted the movement of 鈥� ships of uncertain ownership that help Moscow 鈥� and concluded that it鈥檚 highly likely that Russia is using them as platforms for launching drones.
The report focused on sightings of drones across central and northwest Europe and did not examine , where multiple Russian and Ukrainian attack drones have entered European airspace.
On Dec. 2, the Vezhen, a shadow ship linked to the , sailed in circles off the coast of Ireland when Ukrainian President Volodymyr Zelenskyy arrived for his first official visit, the IISS said. Another ship was nearby, but its signal was off, it said.
At that time, four large military drones were spotted off the Dublin coast, flying for two hours above an Irish navy ship, the report said. The Irish Defense Forces did not reply to a request for comment.
The report cited other sightings that occurred when ships were nearby, several in Denmark.
鈥� On Jan. 3, 2025, as the shadow fleet vessel Arctica sailed along the Danish coast, the IISS said up to 20 drones flew over the port of Koege, Denmark, before disappearing toward the sea.
鈥� On Sept. 22, drone sightings led to the closure of Copenhagen Airport. The IISS found several shadow ships were in the area at the time, including the Arctica and the Boracay.
鈥� Over the next several days, as the Boracay rounded Denmark and several other ships were in the area, more drones were reported over the country, including near military installations.
The IISS said suspicion for at least some of the sightings in September fell on the Boracay. The French military at the end of the month, and President Emmanuel Macron said that the vessel was involved in the drone flights over Denmark.
Denmark鈥檚 Defense Command confirmed that drones were identified in the country鈥檚 airspace in September and October 2025. It didn鈥檛 link them to Russia but noted that Moscow is carrying out hybrid attacks against the West, including those that are of a 鈥渃haracter and scope far beyond what Russia carried out before the war in Ukraine.鈥�
鈥淚t鈥檚 a reasonable assumption鈥� that Russia is launching drones from shadow fleet ships, said Lindfors, though he noted it’s often 鈥渁lmost impossible鈥� to attribute them to one nation or actor.
Russia flew drones above military sites, the report said
The report also concluded that Russia likely tried to monitor military sites in the U.K., the Netherlands, Belgium, France and Germany and force NATO nations to scramble to defend against drones, and so reveal radar positions and gaps in defenses. Among the reports of drones over military installations cited by the IISS were:
鈥� The U.S. Air Force in Europe said there were multiple sightings of drones in November 2024 over four American air bases in the U.K.
鈥� German authorities recorded more than 1,000 suspicious drone sightings in 2025, including over defense companies and military bases where Ukrainian soldiers were training.
鈥� Dutch and said drones were spotted in November and December 2025 over military bases in the Netherlands and Belgium. The IISS said the bases are believed to host American B61 nuclear bombs.
鈥� Drone sightings were , which hosts France鈥檚 nuclear-powered ballistic missile submarines.
The U.S. Air Force in Europe said it couldn’t provide more detail on the incidents in the U.K., the Netherlands and Belgium, nor confirm the presence of American nuclear weapons.
A British defense official, speaking on condition of anonymity to discuss sensitive military information, said a defense police investigation found no evidence to conclusively link the drone sightings in the U.K. to Russia. The Dutch Defense Ministry confirmed drones were seen over Volkel Air Base and said it took steps to defend military sites against drones.
The French army chief of staff headquarters said an investigation of the drones over Ile Longue is ongoing. It didn鈥檛 respond to questions about whether the military suspects the drones were launched from shadow fleet ships.
Requests for comment were also sent to defense ministries in Belgium, Denmark and Germany.
With so many incursions, 鈥渋t would be naive to believe it鈥檚 just a coincidence,鈥� said Lindfors, suggesting that such threats are the new normal.
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Associated Press writers John Leicester, Lorne Cook and Mike Corder contributed.
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