As of March 15th 2021, Space-Available travel aboard DoD and DoD-controlled aircraft remains restricted, except for certain Category I, IV, and VI travel. Details are available in this Table of Allowed Categories.
Regular Space-A (as we know it) for the most common Categories (Active Duty on leave, authorised unaccompanied dependents, retirees) is prohibited except for compelling cases (necessary for humanitarian purposes or due to extreme hardship).
Passebgers with compelling cases require an ETP (Exception to Policy) letter issued by the first O-6 or civilian equivalent in the traveler’s chain of command or supervision. For travelers not assigned to a command, the approval authority is the first O-6 or civilian equivalent with operational responsibility at the travel point of origin.
The temporary suspension remains in effect until further notice.
SOURCE: DoD Memorandum, 15 Mar 2021