Privatization of air traffic control, in essence means allowing the major airlines to have their way with control of all major airports and airspace.  If you like their approach to virtually all other aspects of air travel, this is what you want.  If, like me, you believe that all the corporate genius at United, American, and virtually all our major airlines are brain-dead to anyone and anything but the bottom line, then this is not what you want.  Trump, as usual, paints with a broad and inaccurate brush, in describing our FAA air traffic control.  If 
you are unhappy now with air travel, why would you give control of the entire system to the losers who are responsible?  We have the finest air traffic control in the world-  now.  Can it be better?  Always.  But privatization= major airline control.  Bad, bad idea.