Since 2009, the TSA has not conducted necessary and comprehensive perimeter-security studies.

For the past seven years, TSA conducted “joint vulnerability assessments” with the FBI on perimeter security at 81 of 437 commercial airports during that period, or nearly 19%, according to a Government Accountability Office (GAO) report.

Those reviews covered all 28 of the largest hub airports, which combine to handle more than half of all airline passengers, every three years. Large hubs include airports in New York City, Chicago and Los Angeles. The security reviews also covered more than half – 33 of 57 – of the medium hubs, while neglecting most smaller airports. Medium hubs include Houston Hobby and Kansas City, while smaller airports had less than 380,000 board planes in 2014, such as Charleston, S.C., or Des Moines, Iowa.

"Updating the Risk Assessment of Airport Security with information that reflects this current threat, among other things, would better ensure that TSA bases its risk management decisions on current information and focuses its limited resources on the highest-priority risks to airport security," the GAO report said.

The report said "Incidents of aviation workers using access privileges to smuggle weapons and drugs into security-restricted areas and onto planes has heightened awareness about security at commercial airports. TSA, along with airport operators, has responsibility for securing the nation's approximately 440 commercial airports."

GAO said it was asked to review TSA's oversight of airport perimeter and access control security since GAO last reported on the topic in 2009.

The report concluded: "GAO is making six recommendations, including that TSA update its Risk Assessment of Airport Security, develop and implement a method for conducting a system-wide assessment of airport vulnerability, and update its National Strategy for Airport Perimeter and Access Control Security."

TSA agreed with GAO’s six recommendations, including developing a system for all airports to better gauge their vulnerabilities. “TSA also continues to identify ways to partner and collaborate with industry in performing vulnerability assessments and mitigating risks to transportation security,” Jim Crumpacker, the Department of Homeland Security’s liaison to GAO, said in a formal reply to the report.