Maintenance contractors with the 414th Flight Test Squadron perform engine checks on a test MC-130J at Eglin Air Force Base, Fla.  The aircraft was fitted with vertical fins on each wing, called winglets.  The 413th Flight Test Squadron aircrew and engineers tested the modified aircraft over eight flights.  The goal of the tests was to collect data on possible fuel efficiency improvements and performance with the winglets and lift distribution control system installed.  (U.S. Air Force photo/Samuel King Jr.) - Stock Image