Field Operating Agency (FOA)
A FOA is a subdivision of the Air Force that performs activities beyond the scope of a MAJCOM. The mission they perform is specialized or associated with an AF wide mission. A FOA will usually have the word “agency” in its designator.
It provides special activities outside the scope of a MAJCOM deal with an AF-wide mission. Two examples are the Air Force Weather Agency and Air Force Services Agency.
Direct Reporting Unit
A Direct Reporting Unit (DRU) is a subdivision of the AF that reports directly to the CSAF. DRUs are separate from any MAJCOM or FOA due to unique missions, legal requirements or other factors.
DRU’s perform missions that do not fit into any of the MAJCOMs. Two examples are the USAF Academy and the AF Doctrine Center.
Headquarters Air Force
The senior headquarters of the Air Force consisting of two major entities being the Secretary of the Air Force (SECAF) and the Chief of Staff of the Air Force (CSAF).
SECAF
The SECAF is the head of the Department of the AF. The SECAF is a civilian appointed by the President with advice and consent of the Senate.
CSAF
This person is the highest ranking officer in the AF. The CSAF presides over the Air Staff.
Unified Combatant Commands
Unified combatant commands are composed of forces from two or more military departments, and they have a broad, continuing mission. There are nine unified combatant commands.
Combined Commands
Combined commands consist of forces from more than one allied nation that usually operate under a treaty, alliance or bilateral agreement between the nations concerned. Two examples are the North American Aerospace Defense Command and the Allied Command Europe.