How does being blinded affect a creature who is flying, such as an aarakocra? Would a blind aarakocra risk crashing into things if they tried to fly?
It's up to the table and DM
There really aren't any rules for how being Blinded affects interaction with the environment and movement. Different tables and DMs do different things regarding that, and all can work.
You can allow general knowledge of the terrain (including the air), you can try and ask players to pretend like they don't know where they are and roll randomly for direction, or really anything else that makes table play fun for being Blinded.
No difference between land and air
However, whatever you do choose, there is no difference between flying Blinded or walking Blinded. As long as you keep it consistent after agreement for PCs and NPCs, then I see no problem with whatever is chosen.