Active duty personnel, guard and reserve members and retired soldiers of the U.S. military and certain Department of Defense civilian contractors, along with the spouses and children of all, are eligible for Space Available travel aboard aircraft under the jurisdiction of the United States Department of Defense. Space-A eligible flyers are further divided into six categories depending on the grade of their eligibility or the nature of the trip. A travelers category designation affects his priority status for available flights.
Category I is for members traveling in response to serious illness, impending death or death of an immediate family member. Most uniformed service members and civilian contractors qualify when stationed overseas.
The second category is for environmental or morale leave, including sponsors and their family and DOD Dependent School teachers and their families. Teachers travel is included for school year holidays and vacations.
Category III travelers are typically uniformed personnel on standard leave, permissive temporary duty or those that have been deployed overseas for more than 365 days. The fourth category is for family members of service personnel that have been deployed more than 120 days, dependents under 18 years of age who are joining their parents for environmental or morale leave and teachers on summer break.
Dependent student travel and permissive temporary duty trips that do not involve house hunting fall into Category V. Most travel for National Guard and Reserve members and retired personnel along with the family members associated with each is considered Category VI.