WASHINGTON (Reuters) - President Donald Trump’s proposal to privatize U.S. air traffic control won the backing of major U.S. airlines, but drew criticism from other groups concerned smaller airlines and private companies would lose airport access.

Privatization advocates argue that spinning off air traffic control from the Federal Aviation Administration would increase efficiency and reduce costs, in part by avoiding the government procurement process.

Opponents say the U.S. system, which handles 50,000 flights a day, is so large that privatization would not cut costs, drive up ticket costs and potentially create national security risks. There also are concerns airlines would dominate the private-company board and limit access to airports by business jets.

Airlines for America, the industry trade organization representing American Airlines Group Inc, United Continental Holdings Inc, Southwest Airlines Co and others, praised the proposal.

“This is a bold step that will lead to the governance and funding reforms needed to move our air traffic control infrastructure into the 21st century,” said the group’s Chief Executive Officer Nicholas Calio.

National Business Aviation Association CEO Ed Bolen said the group strongly opposes the proposal, arguing airlines would essentially take run the board. “Small and mid-size towns that rely on access to general aviation for everything from civil services, to emergency support, to business access and more, could have their access to airports and airspace threatened,” Bolen said.

The FAA said in a statement that it welcomes a discussion about the best way to deliver and modernize air traffic services.

Representative Bill Shuster, a Republican who chairs the House Transportation Committee and backs separate air traffic control, praised Trump’s proposal.

“By removing the ATC function from the FAA, Americans will see a more efficient system, flight times decrease, on-time departures increase, emissions reduced, and 21st century technology deployed to guide our planes from gate to gate,” Shuster said.The top Democrat on the Senate Commerce Committee, Bill Nelson, said the proposal will not be approved.

“Scrapping our nation’s air traffic control system is an idea that died in the Senate last year, and it’ll die again this year,” Nelson said. “This proposal would undermine the strong partnership between the FAA and Department of Defense that is so vital to our national security.”

It could take a strong presidential push for the privatization effort. Last year, it failed to get even enough support from Republican members for a vote on the House floor.