The word “air” is used many times in the Bible. It is usually the translation of the Hebrew word “shamayim.” which Strong defines as “the sky,” alluding to the visible arch in which the clouds move, as well as to the higher ether where the celestial bodies revolve; heavens). Birds fly in the air (shamayim).
The word “air” is once used as the translation of the Hebrew word “ruwach” (ruah) in Job 41:16, which says that leviathan’s scales are so close together that air cannot go between them.
The expression “to speak into the air” (1 Corinthians 14:9) is a proverb meaning to speak in vain, as to “beat the air” (1 Corinthians 9:26) means to labor in vain).