Albert Barnes Commentary Ezekiel 1:9

"their wings were joined one to another; they turned not when they went; they went every one straight forward." — Ezekiel 1:9 (ASV)

Two of the wings were in the act of flying, so stretched out that the extremity of each touched a wing of a neighboring living creature, similarly stretched out. This was only when they were in motion. See Ezekiel 1:24.

They went every one straight forward—The four together formed a square and never altered their relative position. From each side, two faces looked straight out, one at each corner—and so all moved together toward any of the four quarters, toward which each one had one of its four faces directed; in whatever direction the whole moved, the four might all be said to go "straight forward."