The head of the Transportation Security Administration appeared to acknowledge in a recent Capitol Hill hearing that only three U.S. airports require employees to go through screening checks before coming to work, even after reports surfaced that dozens of airport workers have potential terror ties.

TSA Administrator Peter Neffenger was asked about the checks at a Senate Committee on Commerce, Science and Transportation hearing on Wednesday.

Sen. Bill Nelson, D-Fla., said only Miami, Atlanta and Orlando require staff to undergo badge checks and screening, and asked: “What about the rest of the 297 airports?”

Neffenger, not disputing Nelson's characterization, acknowledged he had "exactly the same question," while saying they're in the process of improving security.

Nelson, in asking about the protocols, cited increased security measures at the Atlanta airport after authorities broke up a gun smuggling ring in 2014. Prosecutors allege Delta Air workers smuggled guns, including an AK-47, from Atlanta to New York.

Neffenger called the 2014 incident "a wake-up call for America," saying the agency has taken steps to increase worker security across the U.S. Judicial Watch reported that the TSA chief said the nation’s airports will provide a report by the end of the month on vulnerabilities. Judicial Watch also noted, though, that a 2015 advisory committee study said it would be too expensive for most airports to screen industry employees every day.

Nelson was not satisfied with Neffenger's answer.

"That is an insufficient answer in a problem that has been begging now for two years. And the only person that is going to get the airports ... to limit the access into the airports is going to be you and your administration," he said.

The revelation comes shortly after a dozen employees at three U.S. airports were identified as having potential ties to terrorists, according to Freedom of Information Act requests filed by FOX 25’s Washington Bureau.

FOIA requests identified two employees at Logan International Airport in Boston, Mass., four employees at Hartsfield-Jackson Atlanta International Airport in Georgia and six employees at Seattle-Tacoma International Airport in Washington.

But those 12 workers are just a fraction of 73 private employees at airports across the nation flagged for potential ties to terror in a June 2015 report from the Homeland Security Inspector General’s Office.

The 2015 report did not reveal where the 73 workers were employed.

Concerns about airport security in relation to employees were heightened after a terrorist, believed to have been a baggage handler, smuggled a bomb onto an aircraft at Egypt’s Sharm-el-Sheikh airport in October -- 224 people were killed when the bomb detonated shortly after takeoff.