On September 22, air traffic at Copenhagen Airport came to a standstill when as many as three unidentified drones appeared in its airspace, forcing controllers to shut down Scandinavia’s busiest hub and divert dozens of flights.
What could have initially been seen as an isolated disruption soon emerged as the opening salvo in a surge of recent alleged drone incursions across NATO territory—an escalating security crisis exposing serious gaps in European drone defenses and compelling the alliance to recalibrate its strategy.
In the past week, multiple NATO member states have reported mysterious overflights of military installations, airports, and critical infrastructure, prompting governments to scramble their defenses, question the perpetrators’ motives, and warn that a new, low-level form of hybrid warfare may be unfolding over Europe.
From northern Germany to France’s interior, the pattern has become unmistakable: drones of unknown origin operating with impunity in NATO airspace.
“The number, size, flight patterns, [and] time over the airport. All this together indicates that it is a capable actor,” Police Inspector Jens Jespersen said after the Copenhagen sightings. “Which capable actor, I do not know.”
Following repeated incursions, including near Copenhagen, Oslo, Aalborg, and Billund airports, the Danish government announced a nationwide ban on all civilian drone flights from September 29 through October 3.
The measure coincides with Copenhagen’s preparations to host a summit of European Union leaders on strengthening Europe’s common defense and continued support for Ukraine.
“Denmark will host EU leaders in the coming week, where we will have extra focus on security,” Transport Minister Thomas Danielsen said in a statement. “Therefore, from Monday to Friday, we will close the Danish airspace to all civilian drone flights.”
“In this way, we remove the risk that enemy drones can be confused with legal drones and vice versa,” Danielsen said.
However, Denmark isn’t alone in feeling exposed to this recent unidentified drone threat. In Germany’s northernmost state, Schleswig-Holstein, authorities reported multiple drone sightings on the night of September 26.
“Of course, we in Schleswig-Holstein are also investigating every suspicion of espionage and sabotage in this case and remain very vigilant in this area,” Schleswig-Holstein’s interior minister, Sabine Suetterlin-Waack, told Reuters.
That same day, French authorities reported unauthorized drone activity over the Mourmelon-le-Grand military base. French media reported the incident prompted heightened security at the installation, which houses the 501st Tank Regiment and has previously served as a training ground for Ukrainian troops.
Throughout the week of September 22, unidentified drone incursions were similarly reported flying near critical infrastructure in Sweden, Finland, and Lithuania.
Europe has grown accustomed to mysterious drone incursions in recent years. Since Russia’s 2022 invasion of Ukraine, reports of “mystery drones“ appearing near military sites and critical infrastructure have multiplied, surfacing with increasing frequency across the continent.
However, the current wave of sightings is not occurring in isolation. It is unfolding against the backdrop of more audacious incidents earlier in the month. In early September, a swarm of Russian drones breached Polish airspace, a move that Warsaw described as a deliberate probing of NATO defenses. These incidents, along with the recent surge in drone incursions, could have significant geopolitical implications.
The incidents prompted Poland to invoke Article 4 of the NATO treaty, triggering alliance consultations, and catalyzed the launch of Operation Eastern Sentry—a NATO mission to bolster the alliance’s eastern flank.
The multinational defense alliance also announced it was bolstering its presence in the Baltic Sea, deploying multi-domain assets, intelligence platforms, and at least one air-defense frigate. Additionally, Lithuania recently passed legislation allowing its military to shoot down “unmanned drones that enter its airspace unlawfully.“
Despite mounting tensions, NATO has so far refrained from publicly attributing the unidentified drone incursions to any specific actor. Alliance officials have condemned the incidents and vowed to defend the airspace of member states, but emphasize that making an official accusation requires clear evidence and a consensus.
Individual governments, however, have been less restrained. Polish officials explicitly linked the early-September airspace breach to Russian forces, calling it a “deliberate probe“ of NATO defenses.
In Lithuania, senior lawmakers have echoed that assessment, with parliamentary speaker and former Prime Minister Saulius Skvernelis calling for a probe into whether Russia was responsible for incursions in Lithuanian airspace.
In Denmark, both national media and opposition politicians have openly speculated about Russian involvement in the drone incidents. Defense Minister Troels Lund Poulsen described the incursions as a “hybrid attack,“ hinting at Moscow’s possible role without naming it outright.
“Countries or actors have an interest in undermining support for Ukraine,“ Minister Poulsen said at a press conference last week. “It is important that we do not let ourselves be intimidated by that.“
Prime Minister Mette Frederiksen likewise said she could not rule out Russia’s involvement. However, to date, Copenhagen has refrained from making formal accusations against Moscow.
In contrast, Germany has been more forthright in linking past drone incidents to Moscow. Over the past year, German officials have publicly and in background statements to the media accused Russia of orchestrating incursions into German airspace.
Last year, German security sources went as far as alleging that Russia had deployed Orlan-10 reconnaissance drones launched from a civilian shipping vessel in the North Sea. The claim followed a wave of “mystery drone“ sightings over nuclear power plants, land-based liquefied natural gas terminals, and chemical facilities in the Brunsbüttel area.
These earlier incidents led Germany to enact legislation authorizing its military to shoot down “mystery drones“ operating in national airspace. Yet in the current wave of sightings, Berlin has so far not directly named Moscow as the culprit.
Sudden waves of unidentified drone sightings haven’t been confined to Europe. In late 2024, clusters of “mystery drones“ were repeatedly sighted near military installations in the northeastern United States—particularly around New Jersey—sparking headlines and public speculation.
U.S. officials have publicly downplayed the incidents, rejecting claims they were the work of foreign or malicious actors. Nevertheless, an investigation by The Debrief found that drone incursions near U.S. airports from January to March had reportedly increased 25.6% compared with the same period in 2024.
However, unlike Europe, the U.S. has not yet experienced a comparable surge in unexplained drone activity during the recent wave of sightings across NATO countries.
Russia has denied responsibility for the recent drone incidents. “Russia has never had and does not have any such intentions“ [to attack NATO or EU states], Foreign Minister Sergey Lavrov asserted at the UN General Assembly last week. “However, any aggression against my country will be met with a decisive response. There should be no doubt about this among those in NATO and the EU.”
As with previous episodes, the latest wave of drone activity follows a familiar pattern: low-intensity incursions not meant to attack but to observe, probe, and potentially test NATO’s responses.
The ambiguity behind these incidents may be intentional. Probing flights enable the sender not only to observe reactions but also to refine tactics, calibrate response thresholds, and deter escalation by staying below overt war thresholds. In essence, it’s a stress test of NATO’s readiness and cohesion.
As previously reported by The Debrief, this type of enigmatic hybrid warfare aligns with the Kremlin’s official “Information Security Doctrine,“ a concept of Soviet-era offensive information warfare known as “reflexive control.“
According to Russian military doctrine, reflexive control is described as a “massive psychological manipulation of the population to destabilize the state and society.“ The tactic is intended to steer a foreign populace’s decision-making in ways that advance Russian interests.
Seen through this lens, these waves of drone flights may be designed to provoke anxiety, erode public trust in government protections, and pressure NATO leaders into overreacting or revealing weaknesses in their air-defense systems.
Without firing a shot, such operations can shape narratives, influence policy debates, and test the alliance’s cohesion—all key objectives of the doctrine’s emphasis on psychological manipulation and decision-making control.
Yet, NATO and European leaders have so far held firm in the face of these ongoing drone threats. Last week, EU defense ministers agreed to push ahead with a “drone wall“ initiative. This integrated, multilayered border network combines radar, artificial intelligence, jamming, and counter-UAV weapons.
The project aims to strengthen Europe’s eastern flank. However, its success will depend on interoperability, funding, and the rapid deployment of effective systems.
Whether the current wave of drone sightings represents a dress rehearsal for something more serious or merely a test of Europe’s resolve remains to be seen. For now, the pattern of unidentified flights has forced NATO and its partners to confront an uncomfortable reality: the same small, cheap, and deniable systems that have transformed battlefields in Ukraine can also exploit gaps in the alliance’s peacetime defenses.
“The hybrid war is ongoing and all countries in the European Union will experience it,“ Polish Defense Minister Wladyslaw Kosiniak-Kamysz told reporters in Warsaw last week. “The threat from the Russian Federation is serious. We must respond to it in a very radical manner.”
Tim McMillan is a retired law enforcement executive, investigative reporter and co-founder of The Debrief. His writing typically focuses on defense, national security, the Intelligence Community and topics related to psychology. You can follow Tim on Twitter: @LtTimMcMillan. Tim can be reached by email: tim@thedebrief.org or through encrypted email: LtTimMcMillan@protonmail.com