On the surface, privatization sounds like a good thing. One thinks of competition and the market driving innovation. However, "ATC privatization" is not that. It would be giving away the monopoly of controlling US airspace to a disinterested corporation created by our government. This pseudo-private entity, not unlike the "private" Federal Reserve, would be run by the major airlines. The transition would cost taxpayers 18 billion dollars and these assets would be given away for free.
The airline lobbyists claim that our system is broken and even go as far as making outrageous false claims such as not using GPS for airspace control. The truth is the FAA has made GPS available for many years, but the airlines haven't invested in equipping their planes. They claim privatization would reduce delays, yet we all know 90% of delays are caused by weather, something a corporation cannot control. They claim they could transition to NextGen faster than the FAA. Interesting. These are the corporations that failed to invest in replacing their 1970s flight scheduling computers which led to the inevitable system crashes. If the airlines are incapable of even maintaining their own infrastructure, it is unlikely the air traffic control monopoly would have incentive to improve our nation's air traffic system. Our system works and we have the safest airspace in the world. This is not a problem that needs fixing.