Vice Chief of Staff of the United States Air Force

The vice chief of staff of the Air Force (VCSAF) is the second-highest-ranking military officer in the United States Air Force. If the chief of staff of the Air Force (CSAF) is absent or is unable to perform his duties, then the VCSAF assumes the duties and responsibilities of the CSAF. The VCSAF may also perform other duties that the secretary of defense (SECDEF), the secretary of the Air Force (SECAF) or the CSAF assigns to him.

Source: Wikipedia — Vice Chief of Staff of the United States Air Force (CC BY-SA 4.0)