These NOTAMs are… quite disturbing. What military force would operate that close to Italy, in airspace that is managed by Italy under ICAO, and Italy doesn’t know who they are? Nor, I presume what are their intentions? This sounds like it should have led to very serious scrambling of Italian Air Force / NATO quick response force? All states with significant shoreline around these seas (Italy, Slovenia, Croatia, Albania, Montenegro, Greece) are NATO members, and we have an unknown military operating in this “NATO Mare Nostrum”?
Could “unknown” possibly be a clumsy translation from Italian, the intended meaning being “undisclosed” or “unspecified”?
But it also says observed and not scheduled.
Some of this smells like this?
https://en.wikipedia.org/wiki/Itavia_Flight_870
https://www.theguardian.com/world/2013/jan/28/italy-ustica-plane-crash-missile
It was claimed by Italian media that the aircraft was victime of being in wrong place at wrong time (dog fight between Lybia & France jet fighters, Lybia claimed it was one of their pilots had hypoxia, NATO denied they were trying to assassinate Lybian officials who were flying another aircraft nearby…none of the countries were at war and no admit what has really happened but one MIG23 was found on an Italian mountain few days after)
