U.S. Air Force Staff Sgt. Stephen Leonardi, a crew chief with the Air Force's air demonstration team, the Thunderbirds, checks for loose screws on the wing of an F-16 Fighting Falcon aircraft during post-flight maintenance at Royal Air Force Waddington, England, on June 30, 2011. The Thunderbirds are on a six-week European tour during which they are scheduled to perform in nine countries.