Linux Work Progressing on Army's Future Combat Systems.

The Future Combat System is envisioned as a networked 'system of systems" that will include robotic reconnaissance vehicles and sensors; tactical mobile robots; mobile command, control and communications platforms; networked fires from futuristic ground and air platforms; and advanced three-dimensional targeting systems operating on land and in the air.

Boeing and the Army said they chose not to use Microsoft's proprietary software because they didn't want to be beholden to the company or to endure too many system crashes.

Read More Here:

http://www.boeing.com/defense-space/ic/fcs/bia/index.html

http://www.globalsecurity.org/military/systems/ground/fcs.htm