President Trump’s push to move the Federal Aviation Administration’s 14,000 air traffic controllers to a private entity at “no cost” has left aviation groups with more questions than answers.

“This new entity will not need taxpayer money, which is very shocking when people hear that,” President Trump said in a Monday news conference. “They don't hear that too often."

But the idea is based on an old idea that could have costed you more. Alongside The President Monday was House Republican Bill Shuster of Pennsylvania. His bill to privatize air traffic control died last year. Shuster wanted to end a tax on airline tickets that's used to pay controllers.

President Trump wants to fill the gap with fees which airplane operators would have to pay every time a flight needs air traffic control. That means charter flights, helicopters, and recreational pilots—a section of aviation called general aviation that makes up a majority of air traffic nationwide—would pay.

“Anything in terms of impacting the system in terms of cost or safety we should be firmly against,” said Mark Baker, President of the 350,000 member Aircraft Owners and Pilots Association. "Let’s improve what we have, which is pretty darn good. Let’s make it better. But let’s not go backwards on things that are uniquely American.”

Some aviation insiders say airlines could also pay the user fees and pass that onto consumers. So, that begs the question, is this a tax shift or really a tax cut?

The Congressional Budget Office analyzed Shuster’s original bill, saying it would have added $20 million to the national deficit in a decade.

So far, a new bill to match Trump’s announcement has not been rolled out. But aviation groups say they’ll scrutinize a new cost estimate as closely as air traffic controllers watch them.