While I would have liked to find a source other than the Cato institute for it ( https://www.cato.org/blog/trump-pursues-air-traffic-control-... ): The airlines are for it, the key labor union is for it, aviation experts are for it, and the second-largest nation on earth did it. Canada privatized its system in 1996, and today the nonprofit Nav Canada is on the leading edge of ATC efficiency and innovation.
Ah, yes, Cato Institute, that paragon of unbiased, reality-based thought. /s
EDIT: Here is one from the Economist from last year describing NAV Canada in favourable terms as compared to the FAA.: http://www.economist.com/news/science-and-technology/2170347...
And the Wall Street Journal (paywalled): https://www.wsj.com/articles/u-s-canadian-air-traffic-contro...
And the Financial Post (part of Canada's National Post): http://business.financialpost.com/news/transportation/u-s-lo...