Because the military system and the civilian system don't talk to one another. They are two very different systems and when you file IFR out of a military base, they actually transmorgify your flight plan to go outside into the real world where they get your actual clearance. Something else to realize is that even if you're filing from a civilian field to a civilian field in a civilian aircraft, your flight plan info is very different than your ATC info. Not all the info in your flight plan can fit in the ATC system. So basically, you end up w/ three different systems. Military, FSS, and ATC. Sounds cool, but I don't think I'm understanding completely. Will it actually allow you to file from a military field and Ground will have your ATC clearance? If so, that's huge. Much easier to deal w/ than having to play the Base Ops game. I know that's the one big limitation of DUATS.