Air bending and fire bending are two parts to the same whole. Did uncle Iroh teach you NOTHING?!

Airbenders are adjacent to fire and water. Earth is their opposite.(Free element) Fire needs air to survive, water needs air to move. Earth simply stands against the air unwilling to move, potentially harming the earth and the air.

Waterbenders are adjacent to earth and air.(Change element) Fire is their opposite. Water finds its way in both earth and air and brings change and life. Fire is both a danger to and at risk by water through the potential changes it can bring.

Earthbenders are adjacent to fire and water. Air is their opposite.(Stable element) Earth will cradle raging water, and allows fire a place to stand. Over air it simply falls, potentially benefitting the earth.

Firebenders are adjacent to earth and air. Water is their opposite.(Power element) Fire benders spend a lot of time in centering themselves calming their minds, it is here where fire and earth meet. Air is generally necessary for fire to function. Fire is an element that lives and breaths similar to its counterpart water, however it is that life that can destroy fire itself..