The executive officer is the billet of the officer who is second-in-command at the company/battery, battalion/squadron, and Marine Expeditionary Unit (MEU)/regiment/aviation group (i.e., Marine Aircraft Group, Marine Air Control Group, and Marine Wing Support Group) level. Per the "Marine Corps Manual", paragraph 1007.5: "The executive officer shall be an officer of the organization who is eligible to succeed to command, and normally will be the officer next in rank to the commander. As the direct representative of the commander, all orders issued by the executive officer shall have the same force and effect as though issued by the commander. The executive officer shall conform to and effectuate the policies and orders of the commander and shall be prepared to assume command at any time the need should arise." At higher levels of command, the second-in-command is the assistant division/wing commander or, in the case of a Marine Expeditionary Force (MEF), deputy commander. For those commands having a general officer (usually a brigadier general) in command without a designated assistant commander or deputy commander, such as a Marine Expeditionary Brigade (MEB) or Marine Logistics Group (MLG), the chief of staff (a colonel) is the second-in-command. Unlike their U.S. Navy counterparts, XOs of U.S. Marine Corps squadrons in U.S. Naval Aviation do not "fleet up" to become CO.