Speaking as a devout Hindu who takes most of our scriptures at face value and accepts many of their supernatural claims: It is not true that ancient Indian humans had civilization that built aerial flight technology (with the possible exception of, at most, maybe something like a primitive H๏τ air balloon – and I don’t particularly think they built even that, certainly not in any kind of common use beyond perhaps a one-off experimental prototype). No ancient or “mythological” texts or traditions even claim that they did; this is entirely a modern misconception.

The scriptures explicitly and repeatedly state that vimanas were built by the god Vishvakarman, not by humans. Ancient Indian human civilization had nowhere near the industrial capacity to manufacture such things, and the ancient human civilizations described in the scriptures did not possess vimanas, not even among the wealthiest and most powerful kingdoms and armies, unless they obtained one (only one) as a boon from a god or something.

The only exception in the whole history of pre-modern Indian literature is that a single king named Bhoja in the 1000s C.E. wrote that he knew how to build vimanas, but would not describe the method because it was a secret. However there is no record (or even claim) that he ever actually built one, so I must take his claim with considerable skepticism. His immediate descendants were conquered in warfare without ever employing flying machines against their enemies.