Ancient Runways and Flying Fish: Did the Nazca Culture Take Flight? 

I scanned the article and did not see the other distinct possibility for aerial observation: astral projection.  Having read Carlos Castenada and his description of the shamanic usage of peyote, etc. one could consider this possibility.
One does not need drugs to 'astral project', and it's taught to some in our military.  It does vary from remote viewing, but incorporates 'viewing' as a function.

Need I say that it's a ridiculously stupid thing to do? But that civilization was purely demonically driven and what do demons care for humans? Zip. Nada.
(anyone up for a game of 'soccer'? Loser gets to donate his still beating heart.)

But for the gross amount of time we spending studying those 'life suckers', we ought to at least be able to spot them and call them for what they are and what they do.