WASHINGTON — The Transportation Security Administration is tightening security rules for airline and airport workers in the wake of a criminal case in which an Atlanta baggage handler was accused of smuggling guns on commercial jets, Homeland Security Jeh Johnson said Monday.

In the immediate aftermath of the December arrest, Johnson ordered a 90-day review of security measures and now the agency is closing some security gaps the review highlighted.

Among the changes announced Monday are new rules requiring real-time, recurring criminal background checks for aviation workers, including airline employees. Fingerprint-based background checks will also now be conducted every two years for airport employees who hold Secure Identification Display Area badges.

Johnson said airport and airline workers traveling as passengers will also have to go through TSA screening before boarding a flight. The number of access points to secure areas will be reduced to an “operational minimum,” he said.

The security review and subsequent changes were made in the aftermath of a gun smuggling case involving an Atlanta-based baggage handler who was accused of helping smuggle weapons from Atlanta to New York on passenger jets.

Johnson said the security changes will greatly reduce “the potential insider threat” posed by aviation employees.