The meaning of "ruler of the authority of the air" is much debated and that debate will not be resolved here. However, that does not prevent us gathering what facts we can agree upon.
- "Air", when not used literally (eg, Acts 22:23, 1 Cor 9:26, 14:9) denotes the spiritual realm, whether good or bad, eg,
1 Thess 4:17 - Then we, the living remaining, will be caught away
together with them in the clouds for the meeting of the Lord in the
air; and so we will be always with the Lord. [However, some still
argue that this denotes a literal meaning of "air", ie, above the
ground.]
- "Air in Eph 2:2 appears to be equivalent to "heavenly places" as in
Eph 6:12 - because to us the wrestling is not against blood and flesh,
but against the rulers, against the authorities, against the cosmic
powers of this darkness, against the spiritual forces of evil in the
heavenly realms/places. [Compare Eph 1:3, 20, 2:6, 3:10]
Ellicott offers this summary of the theological options:
The prince of the power of the air.—The connection of the “world” with the Evil One as its “prince” is not uncommon in Holy Scripture
(see John 12:31; John 14:30; John 16:11); and the “power” of this
passage is exactly that which Satan claims as “committed” to him in
Luke 4:32. But the phrase “the power of the air” is unique and
difficult. We note
(1) that this phrase signifies not “a power over the air,” but “a
power dwelling in the region of the air.” Now, the word “power” (see
Note on Ephesians 1:21), both in the singular and the plural, is used
in this Epistle, almost technically, of superhuman power. Here,
therefore, the Evil One is described as “the prince,” or ruler, of
such superhuman power—considered here collectively as a single power,
prevailing over the world, and working in the children of
disobedience—in the same sense in which he is called the “prince of
the devils,” the individual spirits of wickedness (Matthew 9:34;
Matthew 12:24). Next
(2), Why is this spoken of as ruling “in the air”? There may possibly
be allusion (as has been supposed) to the speculations of Jewish or
Gentile philosophy; but it seems far more probable that the “air” is
here meant simply to describe a sphere, and therefore a power, below
the heaven and yet above the earth. The “air” is always opposed to the
bright “ether,” or to the spiritual “heaven”; the word and its
derivatives carry with them the ideas of cloudiness, mist, and even
darkness. Hence it is naturally used to suggest the conception of the
evil power, as allowed invisibly to encompass and move above this
world, yet overruled by the power of the true heaven, which it vainly
strives to overcloud and hide from earth. In Ephesians 6:12 the powers
of evil are described with less precision of imagery, as dwelling “in
heavenly places,” the opposition being there only between what is
human and superhuman; yet even there the “darkness” of this world is
referred to, corresponding to the conception of cloudiness and dimness
always attaching to “the air.”
BDAG provides this meaning for "air" in Eph 2:2 -
of the political domain of transcendent beings or powers ... the
ruler of the kingdom of the air, ie, Satan, Eph 2:2 ...
