The 2019 National Defense Authorization Act allows veterans with a permanent and total service-connected Department of Veterans Affairs disability rating to travel space available on military aircraft. Veterans will be assigned a travel priority of Category 6, the lowest priority available, along with retirees and their dependents. Dependents of disabled veterans are NOT eligible for Space-A travel.
Authorized disabled veterans can travel in the continental United States (CONUS) or directly between CONUS and Alaska, Hawaii, Puerto Rico, the U.S. Virgin Islands, Guam and American Samoa. Disabled veterans must have a DD Form 2765, Defense Department ID Card (Tan), in order to fly Space-A.
Space available flights, better known as Space-A or military hops, allow eligible passengers to fill unused seats on DoD-owned or -controlled aircraft. Space-A passengers can fly only after all the space-required passengers and cargo have been accommodated. Space-A passengers are then loaded in priority groups, with emergency leave being the top priority and retirees and disabled veterans rating the lowest priority.
See a full breakdown of all the categories here.
Space-A passengers can take up to two pieces of luggage at 70 pounds each; pets are not allowed. Not all Space-A flights originate from military bases. Commercial airports such as Baltimore-Washington Marshall International and Seattle-Tacoma International also offer Space-A flights.
Long gone are the days of having to show up in person at the passenger terminal to register for a flight. Now, Air Mobility Command, which runs the Space-A program, lets you register for flights via email, and all Space-A terminals have Facebook pages where you can see what flights are coming up and how many seats are available.