Aériens translates to "airy" or "ethereal". It's a beautiful and evocative word that paints a picture of lightness and freedom.
In the song, Grégoire sings, "Il est des chemins inconnus des hommes, si aériens!" (There are paths unknown to men, so airy!). He uses this word to describe paths that are not only undiscovered but also light, perhaps spiritual, and unburdened by earthly concerns, perfectly capturing the song's theme of seeking freedom and following one's dreams.
Grégoire's