The Belgian government has told the BBC it is urgently trying to acquire drone defences after a sighting forced its main airport near Brussels to close temporarily.
Flights were paused at Zaventem airport on Thursday night, after drones were spotted nearby. They were also seen in other locations, including a military base.
"At first, drones flying over our military bases were seen as our problem," Defence Minister Theo Francken said. "Now it has become a serious threat affecting civilian infrastructure across multiple European countries."
Francken said several European allies have offered assistance, and he had accepted help from the German military which is providing anti-drone defences.
About 3,000 passengers of Brussels Airlines were affected by the disruptions, and the carrier said it faced "considerable costs" from cancelling or diverting dozens of flights.
