The CRAF is the Civilian Reserve Air Fleet. This is a scheme whereby in time of war the U.S. Government (the military, really) can assume control of a large number of civilian airliners to transport troops around the world. Essentially, it's a form of insurance or betting; the U.S. Military pays those airlines which choose to participate. The airlines receive preferential military contracts as well as funds to upgrade their aircrafts' cargo and troop carrying capability (heavy duty loading gear, etc). Then, if war comes, those aircraft can be 'called up' by the military for their use. I'm not sure if that includes the use of crews for them.

This is usually a well-debated item in the U.S. military budget, since it seemed to involve paying airlines for not much least until the Gulf War, when the CRAF was actually activated. The military claims it saved a great deal of time by allowing purpose-built miltiary transports to be used solely for carrying military cargo loads the airliners couldn't have shipped.