 AOG also is used to describe critical shipments for parts or materials for aircraft "out of service" or OTS at a location.When an aircraft "goes AOG" and materials required are not on hand, parts and personnel must be driven, flown, or sailed to the location of the "grounded A/C".Usually the problem is escalated through an internal AOG Desk, then the Manufacturer's AOG Desk, and finally competitors' AOG desks.