In August 1964 Closner was assigned to the 494th Tactical Fighter Squadron, Royal Air Force Station Lakenheath, England, where he flew the F-100.

In June 1967 he was assigned to the 615th Tactical Fighter Squadron, Phan Rang Air Base, South Vietnam, as an instructor pilot.

In January 1973 Closner was assigned to the 507th Tactical Fighter Group, Tinker Air Force Base, Oklahoma.

He figured prominently in the command's first F-105 fighter conversion and served as chief of standardization and evaluation, and as an operations and training officer.

In May 1978 Closner became commander of the 917th Tactical Fighter Group at Barksdale Air Force Base, Louisiana, and flew A-37s.