In Revelation 9:2, 'the sun and the air' here signify the light of truth, because 'the sun' signifies love, and the light divine truth. This is why when it says 'the sun and air were darkened,' it signifies divine truth becoming thick darkness. This darkening coming from 'the smoke of the pit' -- meaning that it was caused by falsities accompanying lust.

(References: Apocalypse Explained 9 [2]; Apocalypse Revealed 423)