Senior Airman Ronald Rios loosens the screws holding a fuel filter on a C-130 Hercules engine Dec. 15 at Muniz Air National Guard Base, Puerto Rico. The guidance and control systems specialist with the 156th Aircraft Maintenance Squadron, from Trujillo Alto, Puerto Rico, helps maintain the Air Force's oldest C-130s. (U.S. Air Force photo/Louis A. Arana-Barradas)