Sounds very pretty.
Looks just okay. I don't really like the spelling. The word "air" is too prominent in Airathea, to me.
I think it would be more intuitive, more honest seeming (I think invented or derived names look more dignified if they just go ahead and be deviant, and don't look too deliberately phonetic) if it were spelled Erathea, or maybe Eirathea. Even Erathia.