[@Neo Is Delight]

Don't read this if you haven't seen season 3. [hider=S3 Spoils]After Korra opened the Spirit Portals (Harmonic Convergence), a great awakening swept through the world, granting the ability to bend air to many non-benders. That's how Zaheer gains the ability to escape his prison and free his comrades to ascend to become one of the most talented air benders of all time, before he is defeated by Korra before he can end her avatar cycle.

I assume these new Air benders would be able to pass it along to their kids.[/hider]