An old quip about the Defense Department is that the Navy, Army and Marines all have their own air force. Throw in the Air Force itself and you've got a lot of flying assets. Yet DoD can be surprisingly vague in how it expresses the cost of flight, and how to interpret it. The Rand Corporation looked into this and came up with some recommendations for an activity that costs billions every year. Michael Boito, senior cost analyst at Rand, fills in Federal Drive with Tom Temin on all the details.