Kite question

The word is that kites were invented in China, but they were used in Polynesia in nearly the same time frame. You need something thin (paper or some kind of thin bark or leaves) and something rigid and light (twigs) and clear area (jungle doesn't work) and some occasional stiff winds. And string.

Why didn't the Egyptians figure it out? The question that started this rabbit hole journey Papyrus and reeds should work, and they had string. But papyrus is kind of thick. It might need a bit stronger wind to do anything interesting. And maybe it was too expensive to play with.

Similarly in the Americas": there was paper, but apparently it wasn't plentiful.

Fabric works, if it is thin enough (like silk, see China above). A lot of simple cloth wasn't. Egyptian linen might have been, although "it was coarse compared with modern linen."

Unless you were rich and curious, I guess it would have been hard to experiment with flying things.