(Left to right) Airmen 1st Class Cameron Shank, Tiffany Stroer and Richard Ketchel, 436th Maintenance Squadron crewchiefs, are instructed by Staff Sgt. Alex Asencio, 436th Maintenance Operations Squadron air frame and power plan Phase II instructor May 21. A portion of the Phase II Maintenance Qualifications Training Program requires Airmen to learn how to fill holding tanks with liquid nitrogen to remove oxygen so the fuel does not catch on fire. (U.S. Air Force photo/Airman 1st Class Shen-Chia Chu)