Copy Roll From one Gameobject to another Without other rotations effecting it

So Basically I have two airplanes in 3d space each can be pointing in an arbitrarily different direction. Now what I need to do is find a way to copy only the Roll from one airplane to the other without being affected by any other rotations. I tried just getting the Euler Z of airplane (A) and copying this over to the other. which does initially work. the problem is that any other rotation applied to Airplane (A) will also change the roll value.

I understand this is normal for quaternions but with airplanes, I need to read and set only the ROLL portion around the objects forward Z vectors without being affected by any other rotations.

Is there any way to do this?
Thanks in advance.