Elemental Plane of Air

The Elemental Plane of Air was an Inner Plane or Elemental Plane of the Great Wheel cosmology and the World Tree cosmology models. After the Spellplague, the Elemental Plane of Air collapsed into the Elemental Chaos, mixing with all the other Inner Planes. Air is one of the four elements and two energies that make up the known universe and therefore of keen interest to cosmologists as well as spell casters that wish to harness and wield the raw power of the elements.

Cosmology
According to the Great Wheel cosmology model, the Elemental Plane of Air could be reached via the Ethereal Plane, an adjacent elemental plane, or by an elemental vortex. If traveling through the Deep Ethereal, a blue curtain of vaporous color indicated the boundary of the Plane of Air's Border Ethereal region. Once in the Border Ethereal, a traveler could observe the Plane of Air and be detected by its denizens. Using the spherical model, this plane was adjacent to the para-elemental planes of Ice and Smoke and the quasi-elemental planes of Lightning and Vacuum. Elemental vortices could occur wherever a high concentration or nearly pure form of an element was found, and could be temporary or permanent. A vortex to the Plane of Air could manifest in the eye of a hurricane or in the clean, crisp air atop a high mountain, for example. Temporary gates could be created by the plane shift spell or the abilities of high level druids.

In the World Tree cosmology model, the Astral Plane connected all planes with the Prime Material Plane and the Ethereal Plane was only used for journeying between locations on the Prime. The Elemental Plane of Air was not connected or coterminous with any other elemental plane. The spell astral projection could be used to reach the Plane of Air via a pale blue color pool. Additionally, the gate and plane shift spells could be used to open a temporary portal to this plane.

Description
"It is as open as the eternal sky. It is as solid as a child's breath. It is falling forever."

- Manual of the Planes

The Elemental Plane of Air was filled essentially completely with air but had various impurities that tended to form pockets or bubbles in the otherwise pure atmosphere. Gaseous bubbles included clouds of every type, fog, steam, mist, smoke, poisonous clouds and acidic vapors; also the rare intrusion of elemental fire which is flame without fuel. Liquid impurities were usually water or water-based and tended to form floating spheres when not buffeted or frozen by the winds. Solid matter could be found here, from dust, ash, or sand, to chunks of earth approaching the size of a large asteroid. The larger chunks were often brought into the plane by intelligent beings and were very likely to be inhabited or formerly inhabited.

If you had to describe the Elemental Plane of Air in a single word, it would have been "blue". The very substance of the plane seemed to radiate the magnificent sapphire hue of a clear summer day on the Prime Material Plane. Visibility was twice what the best conditions on the Prime could allow, unless of course something obscured vision. Weather was the primary natural hazard in this plane. The winds were normally light to moderately strong throughout the plane but could intensify into tornadoes, maelstroms, and hurricanes with powerful lightning. These extreme weather events were common, and when other elements got caught up in the storm it could produce pounding rain, blinding snow, pelting hail, freezing sleet, and storms of choking smoke, biting sand, burning ash, scalding steam, or searing fire.

Inhabitants
Invisible, and yet the most common denizens of this plane were the elementals themselves including aerial servants, invisible stalkers and wind walkers. Unless magic was employed their outlines were only vaguely visible if dust or debris were caught in their bodies. When made visible, air elementals were usually large wispy beings with aerodynamic bodies and wings, or propelled themselves by forcing air through their bodies and using fins for maneuvering. Others, sometimes called animentals, mimicked the shape of Prime Material animals and monsters.

Immigrants to the Elemental Plane of Air included the djinn,  some jann, mephits of the air, dust and ice subtypes, and arrowhawks. Reported sightings of other creatures included beholders, belkers, cloud giants, devas, hippogriffs, pegasi, spectres, sphinxes,  sprites, and vapor rats.

Realms

 * Akadi, the Queen of Air, once dwelt in a great maelstrom on this plane.    After the Spellplague, she was revealed to be a primordial and she formed a new realm called Sky Home in the Elemental Chaos.
 * Bahamut was reported to have a citadel here as well as several locations in the Seven Heavens. Whether these were separate realms, the same realm that moved about, or realms that existed simultaneously in these places is still debated.  After the Spellplague, The Lord of Dragons moved to Celestia.
 * Yan-C-Bin, the Prince of Evil Aerial Creatures, once had a realm in the Plane of Air.