1 Corinthians 9:26 ἐγὼ τοίνυν οὕτως τρέχω ὡς οὐκ ἀδήλως, οὕτως πυκτεύω ὡς οὐκ ἀέρα δέρων·
I therefore run like that, as not uncertainly. I fight like that, as not beating the air,
Noun: Accusative Singular Masculine

1 Corinthians 14:9 οὕτως καὶ ὑμεῖς διὰ τῆς γλώσσης ἐὰν μὴ εὔσημον λόγον δῶτε, πῶς γνωσθήσεται τὸ λαλούμενον; ἔσεσθε γὰρ εἰς ἀέρα λαλοῦντες.
So also you, unless you uttered by the tongue words easy to understand, how would it be known what is spoken? For you would be speaking into the air.
Noun: Accusative Singular Masculine

1 Thessalonians 4:17 ἔπειτα ἡμεῖς οἱ ζῶντες οἱ περιλειπόμενοι ἅμα σὺν αὐτοῖς ἁρπαγησόμεθα ἐν νεφέλαις εἰς ἀπάντησιν τοῦ κυρίου εἰς ἀέρα· καὶ οὕτως πάντοτε σὺν κυρίῳ ἐσόμεθα.
then we who are alive, who are left, will be caught up together with them in the clouds, to meet the Lord in the air. So we will be with the Lord forever.
Noun: Accusative Singular Masculine

Revelation 16:17 Καὶ ὁ ἕβδομος ἐξέχεεν τὴν φιάλην αὐτοῦ ἐπὶ τὸν ἀέρα, καὶ ἐξῆλθεν φωνὴ μεγάλη ἐκ τοῦ ναοῦ ἀπὸ τοῦ θρόνου λέγουσα, γέγονεν.
The seventh poured out his bowl into the air. A loud voice came forth out of the temple of heaven, from the throne, saying, "It is done!"
Noun: Accusative Singular Masculine