There where your inv target is local:
_plane = _this select 0;
_invtarget = _this select 1;
while {alive _plane} do
{
_invtarget setPos (_plane modelToWorld [0,0,0]);
Sleep 0.05;
};
LOL, sorry, did click to edit instead of reply, anyway hope this works for you.
Original question:
How to attach an invisible target to a plane?