WASHINGTON — Transportation Safety Administration head John Pistole told a House subcommittee Tuesday that he will continue a controversial program that replaces federal employees with private workers at airport security checkpoints, although he is unlikely to expand it significantly.

After 9/11, the TSA spearheaded a two-year pilot project placing private screeners at five major hubs, including San Francisco and Kansas City international airports. Before 9/11, individual airlines were responsible for recruiting their own security firms to staff checkpoints.

In November 2004, the initiative was expanded into the Screening Partnership Program, allowing any of the 450 airports supervised by the TSA to opt out of using federal screeners and instead seek private companies to provide the same services.

When Pistole was appointed TSA administrator two years ago, he decided to stop accepting applications for the public-private initiative. Currently, 16 airports across the country use contracted screeners, remainders from the pre-Pistole era.

“At the time, I did not see any clear and substantial advantage to expanding the program, though I remained committed to maintaining contractor screening where it then existed,” Pistole said in a prepared statement. “Now, as then, I am open to approving new applications where a clear and substantial benefit could be realized.”

On Monday, the Senate passed a bill that would require Pistole to reconsider applications for private screening that he previously denied. It would also smooth the path for contractors, calling for application approval unless the firm is too pricey or does not meet the same safety standards as federal workers.

At Tuesday’s hearing before a House Homeland Security subcommittee, Pistole said contracted screening can cost between 3 to 9 percent more than hiring federal workers. He repeated to subcommittee members that job performance is comparable between the two types of screeners.

But Pistole continued to express hesitation toward approving all applications that cross his desk.

“The SPP, no less than any other security program, must be implemented in a manner determined by costs as well as demonstrable benefits,” Pistole said.

In a prepared statement, subcommittee Chairman Mike Rogers, R-Ala., called himself a “strong supporter of SPP” but said he was disturbed by recent examples of inefficiency within the TSA.

He pointed to committee data that showed up to 50 TSA employees are on the payroll at some airports employing private screeners. The TSA workers are usually responsible for supervising their private colleagues.

“While we can all agree that strong oversight in this area is critically important, having 50-plus TSA officials at a single airport is just plain overkill and it’s costing the taxpayer huge amounts of money,” Rogers said.

Rep. Sheila Jackson Lee of Texas, the top Democrat on the committee, also was skeptical of the program’s efficiency.

In emergency situations, she said, the TSA can’t mobilize private screeners as quickly as it can federal employees, only one of several flaws with using contracted labor.

Jackson Lee added 9/11 happened “partly on the watch of privatized screeners” and the TSA should not create an environment for it to happen again.

“According to the TSA, operating SPP costs taxpayers more than using the federal screener workforce,” she said in a prepared statement. “In light of that fact and these tight budgetary times, that would be reason enough to support the administrator’s decision not to expand the program. But the list goes on.”

Rep. Dan Lungren, R-Calif., said more airports would apply for private screeners if the TSA appeared more invested in the program.

Lungren scoffed at the idea the TSA has recently added some notable sites to its lineup of privately screened airports.

“You just approved West Yellowstone,” he said to Pistole. “How many flights do they have per day? Have you ever been to West Yellowstone? I have.”

The subcommittee was supposed to hear from other experts, including Mark VanLoh, the aviation director of the Kansas City International Airport, but recessed because the House was voting on legislation.