Can someone educate me please?

With all these airlines(at least 3 that I know of) voting, wanting, threatning to strike. The next step is the NMB. Is the NMB one "national" organization? Or are they local? It seems to me if multiple airlines are all asking for generally the same thing isnt it exactly the job description of the NMB to step in and do something now? Who does the NMB answer to? are they DoT? or another dept?

How has this worked in the past with strikes? Comair, Continental and such?