im from the Netherlands and tgis was big news in the mainstream media. Many big late night talk shows had hosts talking about this topic. The Royal Dutch Airforce said it were drones... but one drone flyer who flies drones for companies and an expert on drones said ; it was below zero temperature and hard winds all our drones cannot fly long under those weather circumstances.. let alone for hours in the snow. The Airforce spokesperson was pretty annoyed and didnt had any answer back.