Is there any difference in Space-A rules regarding eligibility for Active Duty versus Retired service members?

Yes. First of all, Active Duty sponsors personnel have priority (Categories I Emergency Leave (retirees may be added to this category when approved under special circumstances), II EML, III Ordinary Leave, IV Unaccompanied Dependents on EML and V Permissive TDY) on Space-A flights at all times. Other differences include the fact that Active Duty personnel may take their “dependent” mothers and fathers (who have ID Cards DD Form 1173), with them on Space-A trips. Dependent in-laws are NOT included in this privilege. Retired members do not have this privilege, and Retired members and their families travel in Category VI.