Several unexplained sightings of drones over civilian airports and a military base were reported in Denmark last week. Top European leaders will descend on Copenhagen on Wednesday for a European Council meeting to discuss defense and Ukraine, followed by a European Political Community summit in the city the next day. NATO respondsIn response to the unexplained drone flights in Denmark, NATO said on Saturday that it is upgrading defense measures in the Baltic Sea region. The “Baltic Sentry” mission launched in January in response to a string of incidents that damaged power cables, telecom links and gas pipelines on the Baltic Sea bed. Sweden has also pledged to lend Denmark an anti-drone system, though details remain undisclosed, the AP said.