Assistant Secretary of Defense (ASD) for Sustainment Robert McMahon has submitted his resignation effective Nov. 22, after less than one year on the job.

Defense Department Public Affairs Officer Heather Babb confirmed his submission in a Sept. 26 email to Defense Daily, adding, “Mr. McMahon appreciates the opportunity to have served the department both as a civilian and in uniform.”

Assistant Secretary of Defense for Sustainment Robert McMahon is pictured during his visit to U.S. Transportation Command, Scott Air Force Base, Illinois, on July 15, 2019. McMahon serves as one of five keynote speakers at the seventh annual National Defense Transportation Association-U.S. Transportation Command Fall Meeting, October 7 to 10, 2019, Union Station, St. Louis, Missouri. (Photo by Rob Wieland, USTRANSCOM/PA)(

Task & Purpose first reported Thursday that McMahon had submitted his resignation letter to the White House Sept. 17. Babb did not say whether a replacement for McMahon – in either an acting or permanent capacity – had been filled yet.

As the ASD for sustainment, McMahon serves as the principal staff assistant and adviser to Under Secretary of Defense for Acquisition and Sustainment Ellen Lord, Deputy Secretary of Defense David Norquist, and Secretary of Defense Mark Esper on DoD sustainment efforts, and is the principal logistics official within the senior management. He was confirmed by the Senate in November 2018 to the role, which was a newly created office following the split of the Office of Acquisition, Technology and Logistics into the two smaller Offices of Acquisition and Sustainment, and Research and Engineering.

He has been the primary official in charge of driving down sustainment costs for the F-35 Joint Strike Fighter. Back in June, McMahon told reporters at an Air Force conference in Dayton, Ohio, that he was committed to getting the F-35A model to a $25,000 cost per flying hour target by 2025, an achievement considered a stretch goal by other officials (Defense Daily, June 20).

Per the Pentagon, McMahon provides oversight of logistics policies, practices, and efficiencies to enable readiness across the Department of Defense and manages over $170 billion in logistics operations and provides budgetary, policy and management oversight of the Department of Defense’s real property portfolio that consists of 28 million acres, over 500 installations, and more than 500,000 buildings and structures valued at $1 trillion dollars. He previously served as the ASD for logistics and materiel readiness from November 2017 to August 2018.

Before that role, McMahon served as president of Fickling Management Services in Macon, Georgia, and director of field operations and site lead (Warner Robins Air Force Base, Georgia) of the Boeing C-17 Globemaster III Integrated Sustainment Program (GISP), as well as the CEO of the 21st Century Partnership in Warner Robins, Georgia.

McMahon is also a retired Air Force major general with 34 years of service. Immediately before retirement, McMahon served as commander of the Warner Robins Air Logistics Center, Robins Air Force Base, Georgia.

As of Sept. 26, the Pentagon has 13 civilian presidentially appointed, Senate-confirmed (PAS) positions vacant and 17 officials in an “acting/performing the duties of” role.The Senate on Thursday confirmed Air Force Gen. John Hyten to become the next vice chairman of the Joint Chiefs of Staff and Army Undersecretary Ryan McCarthy to become the permanent Army secretary. McCarthy had been acting secretary since his predecessor Mark Esper was confirmed to be defense secretary in July.

The additional acting roles are due to individuals filling in for incumbent officials whose own positions are not vacant, but are themselves performing acting duties for another role.