The Fourth Air Force (4 AF) is a numbered air force of the United States Air Force Reserve (AFRC). It is headquartered at March Air Reserve Base, California. 4 AF directs the activities and supervises the training of more than 30,000 Air Force Reservists. If called to active duty, 4 AF's ready reserve units would be assigned to Air Mobility Command. 4 AF is commanded by Maj Gen Mark A. Kyle.