How to get world velocity on parented rigidbody?

I have a rigidbody with all correct speed read outs. Now ive parented it a great plane, to simulate current, and now the speed read outs are still the same i.e. in local space.

I want to know the speed in worldspace. So that even when i dont move the rigidbody, the speed should read the same as the speed of the moving plane. Does anybodt have solution?

Ive tried transform.transformdirection and GetRelativePointVelocity but both dont seem to work.
Also in the manual its a bit vague and cant figure it out.

Should be able to just add the current object’s velocity to the parent object’s velocity to get worldspace velocity.