Firmament, Sky, Skies
Noun
おおぞら
大空を見ていたら、いやな気もちがふきとんだ。
The unpleasant feeling vanished when I looked up at the sky.
アイリちゃんは大空にうかぶお星さまになったんだよ。
Airi became a star in the firmament.
鷲が大空を悠々と飛んでいた。
The eagle flew leisurely in the heavens.
The big thing in the sky is the heavens. The heavens where birds and planes soar, not the one you go to after you die if you've been really good.
The readings for this word are both kun'yomi readings. You've learned both of these readings by now so you should be able to read this on your own. Just remember that そら becomes ぞら because of rendaku here.