Russia detected a US reconnaissance drone RQ-4 Global Hawk above the Black Sea. The drone was flying at a high altitude towards the Russian border.
US UAVs conduct such flights on a regular basis. The US Air Force has 42 aerial vehicles of the type.
In the autumn of 2016, reconnaissance aircraft P-8 Poseidon of the US Navy with their transponders off tried to approach the state border of the Russian Federation over the Black Sea twice.
Read article on the Russian version of Pravda.Ru