I don't believe I am the only one to have thought of this idea but I haven't heard of anyone exploring the idea or even offcially proposing it.
In a nut shell most people don't like the idea that human flight was even possible thousands of years ago and let alone by cultures that aren't modern and oriented in advanced mathematics. But too many innovations such as harnessing the wind, building effective sea vessels or weapons with exotic aerodynamics have been achieved by ancient civilizations. All of these innovations without the mathematics of hydrodynamics, aerodynamics, thermodynamics , etc. So something about human thinking and problem solving allows the ability to solve complex problems by observation and intuition. So could this innate ability have solved manned flight? This is my question that I think has an answer.
I really love Occam's razor so I'll take the path of least resistance on this issue. So is it easier to fly like a bird or a hot air bag? In 1783 a French man figured it to be a hot air bag or balloon and actually constructed and flew a hot air balloon. How difficult would it be for a culture in Nazca to have developed manned flight with hot air balloons? Nothing technologically prevents this innovation from happening in the past.
While it is known that the geoglyphs can be made without the need for manned flight, the motivation however to make the geoglyphs IMHO does require flight.