Just as modern darts do, medieval military darts have fletching of some kind. A dart just looks like a short arrow with a thicker shaft. (In fact, the arrow is thought to have developed from the dart.)

Being fletched missiles, they fly straight without spinning, just like an arrow does, though perhaps with a bit of fishtailing immediately after the throw as the fletching cancels any sideways momentum caused by the arm's motion. They don't spin end-over-end unless it broke mid-throw.

Just as modern darts do, medieval military darts have fletching of some kind. A dart just looks like a short arrow with a thicker shaft. (In fact, the arrow is thought to have developed from the dart.)

Being fletched missiles, they fly straight without tumbling, just like an arrow does, though perhaps with a bit of fishtailing immediately after the throw as the fletching cancels any sideways momentum caused by the arm's motion. They don't spin end-over-end unless it broke mid-throw.