A member of the Senior Executive Service, McMillin is the deputy chief of warfighting integration and deputy CIO of the Office of the Secretary of the Air Force. McMillin partakes in leading five directorates and four field-operating agencies consisting of more than 1,800 military and civilian personnel and contractors supporting a portfolio valued at $17 billion.

Prior to his current assignment, McMillin was the deputy director of the Air Force staff in Washington, D.C. He began his federal civil-service career in the early 1980s as an auditor with the Defense Contract Audit Agency. He later served as an operations and maintenance budget analyst for Naval Air Systems Command, and as a procurement budget analyst for the Office of the Comptroller of the Navy.

Following those positions, McMillin performed duties as a management support director and executive director at the Naval Plant Representative Office in Melbourne, Australia. He returned to the Pentagon as a budget analyst for the Defense Business Operations Fund in the Office of the Comptroller of the Navy where he stayed until 1992.

From 1992 to 1997, McMillin served as the technical director, then as the deputy director for program analysis and financial management at U.S. Transportation Command. He was appointed to the Senior Executive Service in 1997 as USTRANSCOM’s deputy director for plans and policy.

Later, he was assigned to U.S. Air Force headquarters as associate director of programs in the Office of the Deputy Chief of Staff for Strategic Plans and Programs. He was then appointed director for policy, planning and resources for the Office of Warfighting Integration and Chief Information Officer.