Drone sightings have forced the closure of Aalborg Airport in Denmark, the second such incident this week. Police are investigating, considering various theories, but haven't identified the perpetrators. Several other airports reported drone sightings, but only Aalborg's closure was confirmed. Inbound flights were diverted, and others canceled. The incidents follow similar events at Copenhagen Airport earlier this week and Oslo Airport in Norway. While police haven't ruled out shooting down drones, they acknowledge the complexities involved. The drones involved appear sophisticated, unlike hobbyist models.

Prepared by Rachel Morgan and reviewed by editorial team.