The Floating City of Nym is believed to float due to overaspected corrupted wind crystals forming and tearing the city from the ground sometime during the fall of Nym at the end of the Fifth Umbral Era -- this theory is described in the Sightseeing Log. It's not clear whether this was intentional or accidental. We know less about the Churning Mists and Sea of Clouds, which are vastly older (prob 3rd Era or earlier). This may have been a natural formation: the two zones are prone to overaspecting of wind/lightning aether. Interview touching on subject here.

Alys La flies due to Allagan trickery.

The mechanic shows up in the single-person airship and the Fishing Log's skyfishing. Wind-aspected aether not only has an association with the movement of air, but with raising materials from the ground.