Copenhagen Airport, the busiest in the Nordic region, said it reopened early on Tuesday after drone sightings halted all takeoffs and landings for nearly four hours, with Norway's Oslo Airport also reopening after it had shut its airspace over a drone.

Danish police said that the drones that shut the country's main airport on Monday appeared to have been flown by "a capable operator," adding that no suspects had been identified.

The airports' shutdown left tens of thousands of passengers stranded as flights were diverted.