Air traffic controllers at Washington Dulles International Airport give a firsthand demonstration of the NextGen technology called Data Communications to FAA, UPS and United Airlines officials on Sept. 27, 2016, in Dulles, Va. (Ricky Carioti/The Washington Post)

The debate over whether to remove more than 30,000 air traffic controllers and engineers from the federal payroll got underway in Congress on Wednesday with testimony that efforts to modernize the aviation system have fallen short.

Calvin Scovel III, inspector general for the Transportation Department, said the Federal Aviation Administration has significant problems that might further delay an ambitious modernization plan.

“The FAA’s estimation [for completion] is 2030 at a cost of $36 billion,” Scovel said. “We don’t know what the total cost will be and when it will be complete.”

The fate of more than 30,000 workers — 14,000 controllers and the engineers working on the modernization program known as NextGen — is unclear for several reasons, but none has been as worrisome for Congress as the FAA’s perceived lack of progress in overhauling the air traffic control system.

President Trump has endorsed the concept of separating the 30,000 employees and NextGen from FAA control. The FAA would retain its role as an oversight agency, much like the Federal Railroad Administration, which issues rail regulations and investigates crashes and other railroad incidents.

An effort last year to spin off the controllers and NextGen workers into a private, federally chartered nonprofit organization faltered in Congress, and the new bill under discussion has not been fleshed out in writing.

The makeup of the board that would direct that corporation will be a critical revelation once a bill emerges.

Rep. Peter A. DeFazio (Ore.), the ranking Democrat on the House Transportation Committee, said the new board “would effectively be controlled by the airlines.”

After the hearing, Transportation Committee Chairman Bill Shuster (R-Pa.) said the board’s makeup is “one of the most important parts of the whole thing. Governance of this [new corporation] has to be critical.”

The proposed corporatization has raised concerns among small-plane operators and smaller airports that they will be lost in the shuffle if the focus turns to airlines and their passengers.

Shuster pointed out at the hearing that general-aviation pilots and people served by smaller airports are “constituents” in his largely rural district in southwestern Pennsylvania.

The move to a corporation has been tentatively endorsed by the National Air Traffic Controllers Association, which has argued that spinning off controllers into a private entity would protect them from the threat of government shutdowns and uncertain federal funding.

Union President Paul Rinaldi, in testimony Wednesday, said the union would support the move if the legislation guaranteed current pay rates, and health and retirement benefits for his members.

Shuster concurred, pointing out that if the controllers were dissatisfied with the terms of their transfer to the corporation, about one-third of them are eligible to retire, and their departure could cripple the system.

“Status quo or doing nothing is impossible,” Rinaldi said, with the FAA facing a possible expiration of its funding in September. “We need a reliable funding source.”

But seven smaller unions whose members would be affected sent a letter to committee leaders this week imploring them to “refrain from any attempts to privatize the air traffic control system.”

The committee was reminded that this was not the first proposal to remove the air traffic control system from the FAA.

“Corporatization of the air traffic system is not a radical idea, nor is it a Republican idea,” said Dorothy Robyn, who served in the White House during the Clinton administration. “The federal government is poorly suited to running it.”

A Clinton administration effort to separate the FAA’s regulatory responsibilities from the day-to-day operation of the air traffic control system went nowhere on Capitol Hill.

“I think it would be a mistake to view this proposal as ideological,” Robyn told the committee.

DeFazio and Rep. Rick Larsen (D-Wash.), in a column published last week, acknowledged the FAA’s “rocky start” in modernization efforts but said the agency “is now delivering on the promise to improve our nation’s air traffic control system.”

“We are now on the cusp of a 21st-century system,” DeFazio said at Wednesday’s hearing.

Joseph W. Brown, president of an Ohio propeller company who said he regularly flies his small plane for business, testified that “NextGen is working. It works for me every day.”

About a dozen years ago, the FAA was looking for a catchy name for its multifaceted program to modernize a system that had seen minimal enhancements since radar’s introduction during World War II. Commercial jetliners still move around the country from one designated waypoint to the next, rather than flying in a straight line to their destinations.

The goal was to sell Congress on funding several expensive projects, and the name that was devised to cover all of them was NextGen.

Calling the combined programs NextGen gave the FAA a single name to use when it sought modernization money from Congress. But it also gave Congress a single program to hold accountable when elements of NextGen moved slowly, or not at all.

Congress’s perception that NextGen was moving at a glacial pace was amply bolstered by critical reports from Scovel’s office and from the Government Accountability Office.