Secretary of the Air Force Michael Donley announced Friday he is leaving his job June 21.

Donley has been the service’s top civilian for the last five years and was the acting secretary for seven months prior, making him the longest-serving secretary in Air Force history.

During his tenure, he oversaw a large-scale reduction in Air Force personnel driven in part by budget cuts. “His leadership came during a challenging time for the Air Force, and he helped instill a culture of responsibility, initiative, and professionalism to the service,” Defense Secretary Chuck Hagel said in a statement.

Donley did not immediately announce his future plans, but Hagel said he planned to return to “private life.”