Air's most notable early game spell is Thunderstrike, which requires Air 3 and Evocation 4. It deals significant armor-negating damage to a single square, and lesser area damage and fatigue near it. As such, it is often considered the "gold standard" for evocation magic. Air also has Mistform, which will make the caster highly resistant to nonmagical damage and is a standard thug buff.
Air has a path-boost available: Summon Storm Power, requiring only A1 and Conjuration 2. The catch is that it can only be cast in a storm; Storm is an Evocation 5 spell requiring Air 4 and one air gem to cast. The standard procedure, then, is for one powerful air mage to cast Storm, allowing the army's other air mages to boost their path and then unleash a barrage of Thunderstrikes and Lightning Bolts.
Air has a magic movement spell, Cloud Trapeze.
Like the other elemental paths, Air has Elemental Royalty; the Air Queens require Air 5 and Conjuration 8 to summon, but are themselves powerful Air 5 mages.