Give players Call Down Lightning
Air magic is a spell school that's kind of unwieldly to completely useless at higher levels. Risking hurting yourself or possible summons with Chain Lightning or OoE is oftentimes unacceptable for squishier characters.
A really easy fix would be to add call down lightning as a level 7 or 8 pure Air or Air/conj as a 3x3 upgrade to airstrike. Because the theme for spells often involves a gimmick this couldn't be casted at melee range without giving you considerable arcing damage.
It's similar to stone arrow -> bombard, a direct upgrade with a perfect amount of added complexity.