Lufthansa
The German trade union system was set up after the war on a much more sensible basis than the UK multiplicity of unions (with consequent suicidal demarcation disputes).
Since then German unions have generally understood that it is in their interest for the company to be successful. The presence of union members on the board would therefore be likely to be constructive rather than destructive.
Most British unions have now grasped the principle. Except BASSA of course.