who said it would be possible... doesn't make sense. The reason he could take firebending away from ozai is because there was something in ozai to take away... is aang just going to create the energy to give airbending out of no where?

You might say, "oh he's an airbender, he just gives them some of his energy" WRONG. As the lion turtle said, his own spirit must be unbendable, so if he bended airbending energy from himself... he would die

so someone in another post posted what the turtle said

In the era before the avatar, we bent not the (can't understand this word) but the energy within ourselves. To bend another's energy, your own spirit must be unbendable or you will be corrupted and destroyed

so if that's the quote than my theory might hold true