I am totally new to space-a travel. In brief, what is it?

The Space-Available travel program is a travel benefit that allows authorized passengers to occupy DoD aircraft seats that are surplus after all space-required passengers and cargo have been accommodated. Space-A travel is allowed on a non-mission interference basis only. Space-available travel is a privilege (not an entitlement) available to Uniformed Services members and their dependents. The majority of Space-A flights are offered by the Air Force's Air Mobility Command (AMC) or the Navy and Space-A seats are normally free (there is a tax charged for AMC's Patriot Express flights). The most common destinations are in many parts of the USA (including Hawaii and Alaska), Germany, England, Spain, Italy, Japan, and South Korea. Less frequent destinations (some very rare) could include South and Central America, Africa, and Australia. Usually, the best time to obtain a seat(s) is when dependent children are in school. For more details, read on!