151205-N-YZ751-031 NAS SIGONELLA, Sicily (Dec. 5, 2015) Marine Corps Gen. Joseph F. Dunford, Jr., chairman of the Joint Chiefs of Staff, walks on the flightline during a tour aboard Naval Air Station (NAS) Sigonella, Dec. 5. Sigonella was the first stop of the 2015 USO Holiday Tour, a multi-day, three-continent trip with the 2015 USO Entertainment Troupe. (U.S. Navy photo by Mass Communication Specialist 1st Class Tony D. Curtis/Released)