You are probably referring to "space available" or "MAC" flights. Yes, technically, members of the military are allowed to fly for free on military transports. In practice, however, there are lots of impracticalities that make this very difficult to actually do. First, as you already noted, you have to be somewhere near an airbase that has flights to and from where you want to go. Secondly, it is "space available," meaning that they have to have space for you on the plane, and they DON'T take reservations. The schedule is subject to constant change, and delays and re-routings are common. You basically have to show up at the airbase on the day you want to travel and hope that they have a flight and let you on. That's very hard to do when you are on any kind of schedule. It's a nice idea on paper, and I do know a few people who have used the system extensively, but in 7 years in the Army, I myself have had absolutely zero luck ever using this system. Maybe some of the other active duty folks who post here can give us some advice on how to better take advantage of it.
- R-M-D 2-1-6