I've always been confused by the airbending clouds that the air people and Wan use during beginnings.
It's not an air spout, it's not Zaheer flight, it's not a wind jumpy thing. They just created a cloud, and flew up. It's racked by brain forever what happened to it. But, I think I have an idea about why it was lost. In Beginnings, it doesn't seem the air people have met the flying bison yet. Airbenders learned proper airbending from the flying bison. Maybe, after learning from the flying bison, they realized that the clouds weren't a "real" bending move and thus stopped using it and teaching it. Thus, it was lost to time.
What do you think?