Denmark and Norway faced significant disruptions as unidentified drones prompted the temporary closure of Copenhagen and Oslo airports, halting flights for several hours overnight.
The incidents, which occurred late Monday, affected tens of thousands of passengers, with authorities diverting inbound flights to alternate airports.
The events have heightened concerns across Europe, particularly in nations near Ukraine, amid recent airspace violations involving Russian aircraft.
Danish Prime Minister Mette Frederiksen described the Copenhagen incident as the “most serious attack so far” on Denmark’s critical infrastructure.
While the origin and operators of the drones remain unclear, Frederiksen noted that the episode aligns with recent drone attacks and airspace violations across Europe.
Copenhagen Airport reported sightings of several large drones lingering for four hours, forcing a suspension of all takeoffs and landings.
Authorities are investigating but have not identified those responsible.
In Oslo, similar sightings of lights believed to be drones led to a three-hour airspace closure.
Both airports reopened early Tuesday, though delays and cancellations persisted.
The incidents follow suspected Russian drone incursions into Polish, Romanian, and Estonian airspace, prompting NATO to scramble fighter jets.
Russia’s Kremlin spokesman, Dmitri S. Peskov, dismissed accusations of Russian involvement in the Copenhagen incident, calling them “baseless.”
Denmark, however, is bolstering its military in response to regional threats, with Frederiksen emphasizing Russia’s long-term challenge to European security.