Originally Posted by GlueBall
UAVs operate at +500' altitude levels, just in case of accidental airways infringements.
Sorry, I'm not quite clear - do you mean below the Transition Altitude (whatever that may be in different areas) and at 'half levels' eg. 4500ft alt, 7500ft alt etc., or did you mean 'above FL500' (where they're most unlikely to be spotted, I would have thought.)
Thanks
RC