It was redesignated Fourth Air Force on 26 March 1941 with a mission for the defense of the Southwest and Lower Midwest regions of the United States.

On 29 September 1942, Rice Municipal Airport located in the Desert Training Center was acquired by the IV Air Support Command, and was operational by 26 October 1942.

Re-designated Rice AAF it was used to train pilots and crews of aircraft whose mission it was to support ground troops.

Most P-51 Mustang and P-38 Lightning groups were trained by Fourth Air Force primarily due to the proximity of their manufacturing plants in Southern California.

The command was headquartered at Hamilton AFB, California and originally assigned the region of the CONUS west of the Rocky Mountains, roughly from the Pacific Ocean coast east to the eastern borders of, and .

This reorganization was the result of the need to eliminate intermediate levels of command in ADCOM driven by budget reductions and a perceived lessening of the need for continental air defense against attacking Soviet aircraft.

Units rushed to provide aid and rescue service to the residents of Florida, the Gulf Coast, and the Caribbean in the aftermath of the traumatic and prolonged 1995 hurricane season.

Fourth Air Force units provided assistance for several natural disasters, including the 1994 Northridge earthquake in the Los Angeles area, and the catastrophic midwest floods and the California wildfires in 1993.

Fourth Air Force people were on the first teams into Haiti for Operation Uphold Democracy, and supported Vigilant Warrior and Desert Thunder deployments to Southwest Asia.

The men and women of Fourth Air Force continue to perform international peacekeeping and humanitarian missions on an almost daily basis.

Today the sixty person staff consists of Traditional Reservists, Air Reserve Technicians and civilian employees.