system
Given the following post, respond as if you're commenting on Reddit:
human
[General Superhero Lore] How high would a person have to fly in order to avoid being seen?

Say you just found out that you can fly but you don't want anybody to be able to see you just yet. How fly would you have to fly in order to be invisible to the naked eye? Or how high would you have to fly before you're basically indistinguishable from a bird.

bonus round: If you live in the city, how would you get into the sky without anybody seeing where you lifted off from?

edit: This is receiving more attention than I expected so

bonus round 2: Say you're flying pretty high up, what would you have to do to avoid being seen by other planes while at the same time, being aware where exactly a plane is coming from? I'm thinking you can hide in the clouds for the first part but it might make the second part a bit dangerous. I'd imagine it would be pretty easy to hear a plane but knowing exactly where it's coming from is another matter.
gpt
People don't generally look up, so not very high realistically.

You'd have to be very tiny due to distance to not be seen ever, but if you wore blue/gray, you could probably get away with being 500 meters up.