"Ruler of the kingdom of the air (NIV)" or "prince of the power of the air (NKJV, NASB, ESV)" is an expression for earthly dominion and rulership used by Paul that is only found once in Ephesians 2:2. Cosmology: "Air" to describe everything within and beneath the heavens. The heavens here is not the spiritual heavens where God's kingdom lies, but the heavens that the birds inhabit. This can also be rephrased as everything that is within the bounds of the sky. Source: Discussion in [[Online Courses/BP Heaven and Earth|BP Heaven and Earth]]