Denmark was facing a “high threat of sabotage”, intelligence services said on Tuesday after a “skilled” pilot flew two or three large unidentified drones over Copenhagen Airport, shutting the airspace for hours.
Dozens of flights were diverted and more than 100 cancelled, affecting 20,000 passengers on Monday evening. Terminals reopened at 12.25am on Tuesday when the drones had disappeared, but disruption continued.
“Someone may not necessarily want to attack us, but rather stress us out and see how we react,” Flemming Drejer, director of operations at Denmark's intelligence service PET, told a news conference.
The drone incursion was the most severe attack on Danish infrastructure to date, Denmark's Prime Minister Mette Frederiksen said on Tuesday.
"This is part of the development we have recently observed with other drone attacks, airspace violations, and cyberattacks targeting European airports," she said in a statement, referring to similar drone incidents in Poland and Romania and the violation by Russian fighter jets of Estonia's airspace.
In Oslo, two sightings of drones prompted Norwegian authorities to close the airspace over the city’s main airport shortly after midnight, reports said. The airport reopened after four hours of airspace closure.
Police said nothing immediately linked the Oslo and Copenhagen incidents, but officials would look into any possible ties.
Security concerns in northern Europe are heightened following an increase in Russian sabotage activities and multiple drone and fighter jet incursions into Nato airspace in recent weeks.
The governments of Poland, Estonia and Romania accused Russia of breaching their airspace this month, allegations that Moscow has rejected.
Russia also denied any involvement in Monday night's incident.
At Copenhagen airport, cancellations continued through Tuesday morning.
“Copenhagen Airport has reopened after being closed due to drone activity,” its website stated. “However, there will be delays and some cancelled departures. Passengers are advised to check with their airline for further information.”
Officials chose not to shoot down the drones because they considered the risk too great, with the airport full of passengers, planes on the runways and fuel depots nearby, Jes Jespersen, senior police inspector of Copenhagen Police, said during a news conference.
“You have to think very carefully before starting to try to take down such big drones,” he said. If they were to fall to the ground, “there are planes with people, fuel, and also housing on several sides of the airport”.
Mr Jespersen described the pilot as “a capable actor” and said they seemed intent on showing off and possibly practising their techniques. The drones disappeared after several hours.
There were no signs that the drone pilot intended to cause harm, he added. The drones' lights turned on and off and they appeared to engage in various flight patterns.
“It all indicates that you are not out to attack anyone, but you are out to show off and maybe to practise,” he said of the pilot.
Still, authorities could not rule out the possibility of the drones being part of a Russian hybrid attack, he said. The two or three drones appeared to have flown many kilometres to reach the airport, the largest in Scandinavia.
Police were co-operating with the Danish military and intelligence service in their investigation, Mr Jespersen said.
Investigators are looking at how the drones reached the airport – whether it was by land or possibly on boats coming through strategic straits into the Baltic Sea.
Mr Jespersen said it was not known where the drones were being controlled from, but that it could have been from many kilometres away. The drones were flying from several directions, he said.
“It could very well be something initiated from a ship,” he told Danish broadcaster DR.
In 2023, London’s Gatwick Airport closed its runway for almost an hour after a drone was reported nearby.
In 2018, more than 140,000 travellers were stranded or delayed during the Christmas season after dozens of drone sightings shut Gatwick for parts of three consecutive days.
