Blue Dragon (Earth) Air Domain spells?

[redkobold]

This just seemed inconsistent. The Blue Dragon's subtype is Earth but it can also cast cleric spells and those from the Air, Evil, and Law domains as arcane spells. Why not the Earth domain? Is there a reason for this or is this a mistake in the SRD?

 

[drnuncheon]

Air domain has the lightning spells appropriate for a blue, as well as other weather-related spells you would expect from a desert-dwelling dragon.

Why didn't they make it an Air subtype, then? Not sure, unless they just had an impression of blue dragons as very solid, earthy creatures. Or maybe they didn't want to have two evil air dragons.

J