Is « Shepherd One » really used internationally by air traffic control for Pope's flight?
The FAA declared that as an official call sign for 2015-09-21 to 2015-10-15.



The order it cancels (.pdf here) had the bottom row filled out wrong (SHEPRD1 and "SHEPHERD ONE" were transposed, and "SHEPHERD" was typoed).

A document released on 2016-05-26 lists it in the "deleted special assignment" table (here).



So it's not a permanent reserved identifier in the US; but it might be recurring.

Wikipedia claims here (and here) that in Italy the Papal flights are named "Volo Papale ###", where the ### is a serial number (seemingly the number of times this Pope has flown).  I'll admit that I haven't been able to find anything akin to faa.gov for Italy, France, Australia, or the UK which would corroborate either "Volo Papale" or "Shepherd One".


  Typically, the Pope flies on a chartered Alitalia Jet. The Pope's flight is often nicknamed "Shepherd One" by the press, while the actual callsign is "Volo Papale" (papal flight, in Italian) followed by a serial number.