If your gripe is with the Spanish government or your employer, don't penalise the airlines and passengers that your country relies upon.
So, how else do you propose to make a point to a management who won't listen or negotiate?
One of the basic ideas of a strike is to make the users (i.e. major industries, airlines, passengers) aware of an ongoing problem and get them to bear pressure on the responsible management to resolve the matter, preferably in the best interest of all concerned.
Now, if managers did that in the first place there would never be any need for strikes. Simple really.