The Convention on International Civil Aviation (a.k.a. the "Chicago convention"), includes right from its first version, signed in 1944, an article about "pilotless aircraft". The article in question reads:
No aircraft capable of being flown without a pilot shall be flown without a pilot over the territory of a contracting State without special authorization by that State and in accordance with the terms of such authorization. Each contracting State undertakes to insure that the flight of such aircraft without a pilot in regions open to civil aircraft shall be so controlled as to obviate danger to civil aircraft.
The original text is available here.
I would guess that language like that (which it takes time and effort to produce) will not get included in an international treaty without a reason.
So the question is, which aircraft did the authors of article 8 have in mind in 1944?