Mysterious drone flights in NATO airspace have caused alarm across Europe. Here's what we know

Mysterious drone flights over the airspace of European Union member countries in recent weeks have alarmed the public and elected officials. Intrusions into NATO’s airspace, some of them blamed on Russia, reached an unprecedented scale last month. On Sept. 10, a swarm of Russian drones flew into Poland's airspace, forcing NATO aircraft to scramble to intercept them and shoot down some of the devices.