The House next week is scheduled to vote on a bill to privatize about 65 percent of the workforce at the Federal Aviation Administration.

More than 30,000 people — no one is quite sure of the exact number — would be shifted into a private, nonprofit corporation responsible for directing and modernizing the movement of airliners and private planes.

The planned vote comes a month after the Transportation Department’s inspector general again criticized the FAA for failing to fully deliver on its modernization efforts. Spurred by several critical reports from the inspector general and the Government Accountability Office, Congress has become increasingly frustrated with the agency’s failure to implement the $36 billion Next Generation Air Transportation System, known as NextGen.

“The government’s continued promises and claims about NextGen benefits are not based in reality but on a lot of smoke and mirrors,” said Rep. Bill Shuster (R-Pa.), chairman of the House Transportation Committee and the prime mover behind the effort to transfer the FAA workers.

In the face of Democratic opposition in the House and bipartisan foes in the Senate, Shuster devoted the summer to persuading those who will vote on the House floor. President Trump’s endorsement of the plan earlier this year and Shuster’s growing clout within the House GOP helped motivate House Speaker Paul D. Ryan (R-Wis.) to bring the bill to a floor vote.

Rep. Peter A. DeFazio (D-Ore.), the ranking Democrat on the Transportation Committee, took the House floor Thursday to denounce the planned vote. DeFazio repeated his stance that the airlines would come to dominate the private corporation’s board, revoke the 7.5 percent ticket tax they despise and replace it with a more regressive per-passenger tax.

DeFazio released a new GAO report that said the “FAA is taking actions to address challenges within its control” and that the cost of NextGen has “evolved, but not increased markedly since 2004.”

“The FAA is doing an excellent job,” DeFazio said. “Seven to 10 years ago I never would have said that, but they’ve gotten this straightened out over the last seven years. The [NextGen] system is on time, on budget, and privatization would delay the modernization of the system.”

The GAO’s Gerald L. Dillingham, who has produced several reports critical of the NextGen program, said in the report that DeFazio released Thursday that privatizing the modernization effort could provide greater financial stability for the program, because funding would not be subject to the federal budget process.

But he said transitioning between the FAA and a nonprofit board, despite provisions in the bill to smooth that transfer, could be problematic.

“According to FAA, the transition could create some uncertainty among some employees over future workforce or organizational changes,” he wrote.

Given the magnitude of the investment by the federal government and the airlines, which would need to put billions into equipping their planes, the NextGen program has been scrutinized repeatedly.

The FAA came under criticism from Inspector General Calvin L. Scovel III again last month, who said in a letter to the Transportation Committee that the benefits the FAA says NextGen will provide are “overly optimistic.”

The House plans to meet just eight more times this month, and FAA funding is set to expire on Sept. 30. The Senate Commerce Committee has approved a bill that does not include splitting up the FAA.

Given Senate opposition to the plan to split up the FAA, there had been expectation that Congress simply would extend FAA funding at its current level rather than grapple with competing bills.

Shuster’s bill proposes a 13-member board with two members appointed by the secretary of transportation and two members selected by the other board members. The rest of the panel would be composed of one member each from the major airlines, the regional airlines, the cargo airlines, small-plane owners, corporate plane operators, the air traffic controllers, the airports, commercial pilots and the corporation’s chief executive. That chief executive would be selected by the board.

Correction: An earlier version of this article said reports critical of the FAA came from the General Services Administration. They came from the Government Accountability Office.