The first part of President Trump's $1 trillion infrastructure plan took flight Monday when the president called for the privatization of the country's air traffic control system. "We're still stuck with an ancient, broken, antiquated, horrible system that doesn't work," Trump said of the current air traffic control organization run by the FAA. "Other than that, it's quite good."

Flights are delayed and flying sucks, the president argued, and the best way to change that is to take the responsibility for managing airspace away from the bureaucrats at the Federal Aviation Administration and hand it over to a private nonprofit organization. Such a plan won't cost taxpayers a dime, he said, and will improve efficiency.

This idea dates to the 1970s, but has never gotten anywhere. Representative Bill Shuster, the Republican chair of the House Transportation and Infrastructure Committee, brought it back last year, but his legislation stalled in the Senate. But the White House is confident it can push it through this time. It's also a test drive for the administration's larger embrace of public-private partnerships. “Shuster did a really good job of pulling together a package and having that ready to go,” said D.J. Gribbin, an infrastructure policy specialist on the White House National Economic Council.

Although airlines generally love the idea, not everyone believes privatization is a smart move. Let's break it down.

What is Trump suggesting?

Trump wants to hand over the nation's air traffic control infrastructure to a private, nonprofit entity with its own board made up of airlines, unions, airports, and federal officials (like a real company!). The administration has not offered a lot of details on how this might work, but promises the change would not increase costs or decrease safety. The International Civil Aviation Organization, the United Nations’ international air navigation body, has said an “autonomous authority”—like a separate air traffic control organization—in charge of its own finances and management could modernize more quickly, increasing safety overall.

The FAA would oversee this new nonprofit entity, which would be funded through user fees—like takeoff and landing charges—instead of the excise taxes on passenger tickets and fuel that currently fund the country's aviation system. Moving air traffic controllers from the FAA to this new organization would take about three years, the Trump administration estimates.

Why would anyone want this?

Some people don’t! (More on them later.) But the Trump administration says revamping air traffic control would increase efficiency, reducing delays and other snafus. The reform is necessary, it argues, because modernization efforts have stalled even as the number of American travelers has ballooned to 700 million a year. And a dysfunctional Congress has not helped: Between government shutdowns and uneven funding patterns, reform proponents argue the FAA can’t count on the money needed to make changes.

Has this worked for other places?

Yes. In at least fifty other nations, including the UK, Canada, and New Zealand, privatization or partial privatization has largely succeeded, with a 2009 study finding more efficient flights and fewer delays. But there have been some hiccups, and a bunch of open questions. The UK government had to bail out its air traffic control organization when the airline industry took a hit after the terror attacks of September 11, 2001. And a US government study that examined six nations that had made the switch “concluded that this change in safety oversight required a culture shift that was difficult and also requires strong data collection and quality-control procedures.” Remember, too, that the American air traffic control system is very big—big league, even. So it's hard to compare other countries' experiences with what could happen in the US. The White House and FAA will have to be careful, calculating, and deliberate while setting up this other body, and that will not be not easy-peasy.

What does this mean for me?

This is not entirely clear. The Trump administration has touted reduced delays, but it’s hard to blame delays solely on the FAA or air traffic control operations. First, bad weather is a thing. And airlines themselves contribute mightily to the problem with late crews, overbooking, and system-wide computer glitches (hello, Delta). Researchers say smart logistical fixes, like changing how planes queue up when departing, could alleviate delays.

That's not to say privatization won't help the situation. Newer tech could help fight congestion—and thus flight delays, too.

Who’s into the reform?

Most big airlines are very cool with this, as are small government folks. (Delta is the exception, arguing the move will hike ticket prices and distract from air traffic control modernization work.) The air traffic controllers union is also mostly on board.

Who hates it?

All of this makes rural airports, communities, small airlines, and general aviation enthusiasts nervous. Most worry about new user fees, which could place a larger burden on smaller operators who don’t enjoy economies of scale. A small survey released in February by a coalition of these stakeholders found that 55 percent of American voters “are currently very pleased with the performance of the FAA and see no reason to privatize it."

Congressional Democrats also aren't too jazzed with the idea. "Selling off our air traffic control system threatens passenger safety, undermines the FAA's ongoing modernization, jeopardizes access to rural airports, and adds to the deficit," said Representative Nancy Pelosi.

Uh, what do air traffic controllers do anyway?

The FAA’s Air Traffic Organization employs about 6,000 technicians and 14,500 air traffic controllers who run the country’s airport towers and terminal areas. These guys and gals direct aircraft through American airspace from their perches on the ground. “These people are artisans—they really are,” says Sid McGuirk, a former air traffic controller who now a professor at Embry-Riddle Aeronautical University

It’s true that the air traffic control system is due for an upgrade. (At Monday’s White House announcement, Shuster waved the paper “flight progress strips” that controllers still use to keep track of planes in the air.)

Fortunately, the FAA has been working on a $35 billion one for nearly 15 years. The NextGen system would nix radar-based aircraft tracking in favor of GPS, controllers’ voice commands for digital ones, and would phase in more advanced flight planning software. (Many major airlines have started this transition.) The updates would allow airlines to plan more direct and faster routes. They would also make the whole air traffic control system more efficient. The target date for the changes is 2030, but the NextGen program has missed key deadlines for years now. Meanwhile, advances in artificial intelligence could eliminate many of the more routine elements of the job. “The closer we get to AI, the more likely it is that machines will do the normal day to day operations, and people will monitor and intervene,” says McGuirk.

Which is all to say: Whatever happens with this White House push, the air traffic controllers’ jobs will look very different in a decade or two.