Transportation Secretary Elaine Chao distanced herself from President Donald Trump’s searing assessment of the U.S. air-traffic system in her testimony before a House committee on a plan to strip it out of government.

"They are protecting our safety," Chao said Thursday in response to a lawmaker’s question about Trump’s criticism of the performance of the Federal Aviation Administration’s air-traffic controllers. "Those are not my words."

Chao stood with Trump on Monday at a White House ceremony in which he endorsed splitting off the FAA’s air-traffic system and placing it under a non-profit corporation. The president repeatedly attacked the existing system. He called it “horrible," saying it had wasted billions of dollars and used outdated technology. He contended its leaders didn’t know what they were doing.

"You stood right there next to him and yet what we’re hearing from you today is a little different,” Representative Dina Titus, a Nevada Democrat, said to Chao at a hearing before the House transportation committee. "So I’d like to go back over some of the things and see who we should believe."

"I believe that the FAA is doing a good job," Chao said. She was testifying at a House Transportation and Infrastructure Committee hearing and stopped short of directly criticizing her new boss in the White House. "You heard the president. He has spoken," she said.

Chao is a long-time Republican loyalist, having served in the administrations of President George W. Bush and his father, George H.W. Bush. She is married to Senate Majority Leader Mitch McConnell.

She has vigorously defended the Trump plan at two Congressional hearings in two days, sometimes under aggressive opposition from lawmakers of both parties.

“It’s a big step,” she told the House committee Thursday. “But after 30 years of debate, we believe the country is ready.”

Chao said she believes air traffic would be more efficient under private oversight.

At a separate event in Washington, Southwest Airlines Co. Chief Executive Officer Gary Kelly agreed, saying the current system is at risk of mounting inefficiency and higher costs due to bottlenecks in air-traffic capacity.

Kelly said he is optimistic about the proposal because of the support from the administration and said concerns about privatizing air-traffic control can be addressed. Republican and Democratic lawmakers have worried that smaller communities being disadvantaged under a privatized system, concerns that Kelly said are "not on point."

Southwest has already had to reduce service in smaller markets due to low traffic levels, Kelly said. Smaller airports and communities are most at risk of seeing flights cut due to air capacity constraints under the current system, Kelly said, adding that a modernizing air-traffic control through privatization would be "far superior for the smaller communities."

"It’s just human nature that you’re going to cancel those flights with the fewest number of passengers," he said. "That’s the way it works today, so they’re already being harmed."