Rep. Bill Shuster, R-Pa., shot back against the American Conservative Union Foundation after the group came out against the lawmaker's plan to privatize air traffic control.

The ACUF argued the proposal would not truly privatize the agency but Shuster's spokesman said the determination didn't make sense and wasn't shared by most other conservative groups.

"It's a shame ACU doesn't recognize the conservative merits of the 21st Century AIRR Act — which reduces the size of government, cuts taxes on the traveling public, and reduces wasteful government spending — unlike many prominent conservative and free market groups that support the bill," said Justin Harclerode, spokesman for the House Committee on Transportation and Infrastructure, which Shuster chairs. "This fully independent, private entity will not be governmental, or public-private, in any way."

Harclerode then rattled off a long list of right-leaning groups that did back the legislation, including Heritage Action, FreedomWorks, Americans for Prosperity, Competitive Enterprise Institute, Citizens Against Government Waste, National Taxpayers Union, Reason Foundation, Taxpayers for Common Sense, Alliance for Transportation Innovation, and American Legislative Exchange Council, among others.

Shuster's legislation would take air traffic control out of the Federal Aviation Administration and instead create an independent nonprofit to run it. It would be governed by a board including the transportation secretary, people nominated by the airline companies and representatives of the air traffic controllers' and pilots' unions. The board would be funded through user fees. Shuster and other fans argue a non-government entity would be better suited to keep the technology up-to-date. The legislation is expected to be taken up this fall.

In a surprise announcement Thursday, the ACUF said the legislation "misses completely" because the resulting entity wouldn't be completely private. It argued that Shuster's plan "raises serious questions as to how this transfer of power would work: the U.S. Secretary of Transportation would be given the authority to decide the makeup of employees and approve the fees to fund operations while the Board of Directors, which would include directors appointed by the government, would have to accept existing union contracts."

The ACUF is a branch of the American Conservative Union, one of the main groups on the right the rates lawmakers based on their votes. The ratings are commonly used to determine how conservative a lawmaker is. A source at the ACU said it had not yet decided whether a vote on the 21st Century AIRR Act would be one of the "key votes" it uses for its annual evaluations.

Harcelrode said he "definitely wanted to make the point" that the ACUF's position made it the odd man out among conservative groups. "Heritage Action, for example, is key voting the bill," he said.