Airports in Copenhagen (Denmark) and Oslo (Norway) were closed for several hours after large drones were reported near the runways.
Operations resumed on Tuesday morning, but flight delays and cancellations continue, affecting thousands of passengers.
At Copenhagen, the busiest airport in northern Europe, traffic was suspended for four hours after two or three drones were seen flying around the runways, as reported by Reuters. According to the police, they appeared to be operated by "a competent actor."
"It is an operator who has the capabilities, the will, and the tools to act in this way," said Commissioner Jens Jespersen.
He emphasized that the drones came from different directions and turned their lights on and off before disappearing.
The incident led to the diversion of 31 flights to other airports in Denmark and Sweden and caused delays or cancellations for approximately 100 flights, affecting around 20,000 passengers.
Following the reopening, airport management warned that delays and cancellations will continue and urged passengers to check information directly with the airlines.
Copenhagen Police and the Danish Security and Intelligence Service (PET) warned that the reported incident represents "a very serious situation." Flemming Drejer, PET's operational director, acknowledged that given the international context, Denmark faces an increased level of sabotage threat. "All possible options and connections are being considered," he stated, according to The Guardian.
Similarly, Anne Tønnes from the Copenhagen Police emphasized that the incident constitutes a serious violation of Danish law.
The Danish press notes that Tønnes repeatedly referred to the incident as an "attack," mentioning its impact on the country's critical infrastructure.
Oslo Airport, closed for three hours
In Norway, Oslo's Gardermoen international airport was also closed for nearly three hours after similar drone sightings. All flights were redirected to the nearest airport, and the airspace was reopened around 03:22, announced airport operator Avinor.
Danish and Norwegian authorities announced they would cooperate to determine if the two incidents are related. "It is too early to say if there is a connection," stated Deputy Police Commissioner Jakob Hansen.
These events come amid repeated disruptions in European airports. Over the weekend, a cyber attack on Collins Aerospace systems affected airports in London, Berlin, and Brussels.
Drone incidents were also reported last week at other European airports. At Otopeni, last Friday, a small civilian drone was detected 3.5 kilometers from the runway, and a week ago, Polish authorities announced they neutralized a surveillance drone in Warsaw, operated by a subsequently expelled Ukrainian citizen.