Staff Sgt. Daniel Maas carefully operates the boom of a KC-135 Stratotanker. U.S Air Force Staff Sgt. Daniel Maas carefully operates the boom of a KC-135 Stratotanker to refuel one of seven F-16 fighter jets returning to Eielson Air Force Base, Alaska, from Kunsan Air Base, Korea, on Jan. 20, 2008. Maas is a boom operator with the 909th Air Refueling Squadron. SHARE: Download: Full Size (0.02 MB) Credit: VIRIN: 534367-P-ZRZ48-301.jpg Photo Gallery