Normal Air Runes need a Skystone along with a Blank Rune; a Silver Ingot and three Weak Air Runes to make one Normal Air Rune.
Normal Runes can be crafted at level ten at the Rune Altar.
You need three of these to learn Wind Slash and you will need extra to cast the spell.
The command to make a Normal Air Rune is [nya!rpg rune altar air]. For more info use [nya!info normal air rune].