Flying through the air.

synonym: in flight.

Roget 293: whence, hence, thence; with a foot in the stirrup; on the wing, on the move.   

Roget 270: from hand to hand, from pillar to post.    on the way, by the way; on the road, on the wing, under way, in transit, on course; as one goes; in transitu [Lat.], en route, chemin faisant [Fr.], en passant [Fr.], in mid progress, in mid course.    ... show more

Roget 264: under way; on the move, on the wing, on the tramp, on the march.   

Roget 267: under way, under sail, under canvas, under steam; on the wing, in flight, in orbit.