What does CO mean in the Army?
Commanding officer
The commanding officer (CO) or sometimes, if the incumbent is a general officer, commanding general (CG), is the officer in command of a military unit. The commanding officer has ultimate authority over the unit, and is usually given wide latitude to run the unit as they see fit, within the bounds of military law. In this respect, commanding officers have significant responsibilities (for example, the use of force, finances, equipment, the Geneva Conventions), duties (to higher authority, mission effectiveness, duty of care to personnel), and powers (for example, discipline and punishment of personnel within certain limits of military law).
Air officer commanding
In the United States Air Force, the term "Air Officer Commanding" is used specifically to refer to the specially selected officers who command cadet squadrons and groups at the United States Air Force Academy in Colorado Springs, Colorado. In the case of a cadet squadron, the AOC is normally a major; in the case of a cadet group, the AOC is normally a lieutenant colonel. These officers exercise command authority over their cadet units and are expected to train cadets in officership and military matters, advise the cadets who hold leadership positions in the unit, and act as role models for the future officers.