This effort is continuing as DARPA’s Vulture II, but the program has been re-scoped and as a result of that, Boeing is not building a demonstrator, aka SolarEagle.
These artist’s concepts are no longer applicable to the program as of January 1, 2013.

Continuing the tradition of world-leading "Eagles," Boeing Advanced Systems and partner QinetiQ have named their entry in the Vulture air vehicle program the SolarEagle. Vulture is the Defense Advanced Research Project Agency’s ultra-long-endurance aircraft program. In spring 2007, the team was awarded a $3.8 million Defense Advanced Research Projects Agency (DARPA) contract for Phase 1 of the program, an effort to create a new category of ultra-long-endurance aircraft. Boeing/QinetQ photo.