A U.S. Air Force C-17 Globemaster III prepares to take off during the U.S. Air Force Weapons School mission employment exercise, Dec. 4, 2011, at Nellis Air Force Base, Nev. The two-week-long mission employment phase is the final part of a five-and-a-half-month Weapons School graduate course that showcases the students newly acquired skills to test their ability to plan, execute and lead complex missions.