What kind of travel orders require a Unique Control Number?

Unique Control Numbers (UCNs) are specifically associated with Space-Available (Space-A) travel orders, which allow eligible travelers to board military flights on a non-revenue basis when space is available. The system for managing Space-A travel requires precise tracking and documentation to ensure that orders are processed correctly, which is why a Unique Control Number is allocated for each travel order in this category.

This requirement helps in monitoring and validating Space-A travel requests, maintaining overall organization and efficiency in military transportation logistics. Other categories of travel orders, like business or emergency travel orders, do not necessitate the same level of tracking with UCNs because they follow different protocols and serve different purposes within the military travel framework.