This one has been rustling my jimmies for quite a bit now. Whenever I fly a plane in Multiplayer, it's only a matter of time before this severe bug happens: the player flying the plane can end up "falling" out without it being computed in the server. The client can move around freely but cannot interact with things that they are looking at, only things that they would be looking at if they were in the plane. The bug also affects chunk loading, chunks will load as if the player is still in the plane. The server will still act like the player is in the plane.

Here's an example: if I "fell" out of the plane, went 50 blocks away, looked to the left of the direction the plane was heading, and shot a gun, the bullets will spawn to the left of the seat of the plane.

Duplicate of #22