You probably want to match the plane's speed and position with the camera, rather than manage the plane's speed.
If you are tracking the plane as it moves, remember that you can use camSetTarget to always look directly at it. If you don't want to look directly at it, you could use something like:
_camera camSetTarget _plane;
_camera camCommit 0;
_camera camSetTarget (_plane modelToWorld [_xOffset, _yOffset, _zOffset]);
_camera camCommit 0;
_camera camSetTarget _plane;
_camera camSetRelPos [_xOffSet,_yOffSet,_zOffset]
_camera camCommit 0;
Put any of those inside a waitUntil loop and you will get less jerkiness than if you put them inside a while/sleep 0.01 loop