The Executive Officer, also known as the XO, First Officer, or Number One, is the second in command of a starship.  Traditionally, it is held by an officer of the rank of Commander or Lieutenant Commander.

In STARFLEET International, the Executive Officer is the second in command of a chapter.  When the CO is temporarily unable to carry out certain duties, they step in and cover those duties making certain that the monthly reports are handled as well as the needs of the chapter are handled during the CO's incapacitation.  Should something happen to the CO, they are the one who step into the position of CO.

Aboard the USS Alan Turing is Commander James Sheldon. (picture coming soon)