All those things sound nice, but to skeptics of the proposal, converting the air-traffic control system into a not-for-profit cooperative isn’t necessary to achieve them. The key to reducing delays and increasing efficiency, they say, is not a bureaucratic overhaul but the full implementation of technology known as NextGen that is shifting air-traffic control to a satellite, GPS-based system. The shift has been slow and costly, which has led Republicans to call for getting the government out of the way. But air-traffic control, per se, isn’t the problem, and despite the outdated technology, the system’s safety record remains strong. “If something isn’t broken, why fix it?” asked Paul Hudson, a member of an FAA advisory committee and the president of a passenger advocacy group called FlyersRights.org.

Critics of privatization say it would give even more power to airlines, who largely back the idea. Funding for air-traffic control would shift from the collection of taxes on fuel and airline tickets to a user-fee model that would be established by a 13-member board. “Essentially you’re going to be privatizing the power to tax,” Hudson said.

Mark Baker, president of the Aircraft Owners and Pilots Association, said the trade group representing non-commercial aviators had heard “no complaints” about air-traffic control and would oppose new users fees. The idea also has critics on the right, who lamented that converting air-traffic control into a nonprofit was not true “privatization” and risked creating a new quasi-governmental entity like Fannie Mae or Amtrak that would require taxpayer bailouts if it failed.

Trump and his advisers argued that spinning off air-traffic control from the FAA would expedite the deployment of NextGen technology while freeing the agency to fulfill its core function as a safety regulator. “You have what is in essence a technology business embedded in a governmental agency,” said D.J. Gribbin, the president’s top infrastructure adviser.

To some extent, the momentum for privatization has grown out of frustration with Congress, which has been sticking the FAA with short-term extensions rather than long-term reauthorizations that provide the stability the industry wants. The industry has suffered from a shortage of both pilots and air traffic controllers, and the need for a stable funding stream has led the National Air Traffic Controllers Association to endorse privatization as long as the union’s contract is honored.

Where Trump and his critics agree is that his embrace of privatizing air-traffic control is emblematic of his larger, details-still-to-come infrastructure plan. For one, it’s relatively cheap. “This new entity will not need taxpayer money, which is very shocking when people hear that,” Trump boasted on Monday.

In a victory for conservatives, the president is no longer touting new public investments on a grand scale; the $1 trillion he once promised has fallen to just $200 billion in direct federal spending. Instead, he’s relying on ideas Republicans have already proposed to incentivize private development and reduce the federal role in infrastructure altogether. The president plans to promote his infrastructure plans on the road in Cincinnati on Wednesday and again back in Washington later in the week, but he is expected to focus on permitting reform rather than new federal money.