FILE PHOTO -- A B-2 Spirit from Whiteman Air Force Base, Mo. pulls up for a fill-up with a KC-135 Stratotanker of New Jersey's 108th Air Refueling Wing, Air National Guard over Kansas farmland. The KC-135 Stratotanker's principal mission is air refueling. This asset greatly enhances the U. S. Air Force's capability to accomplish its mission of Global Engagement. (U.S. Air Force photo by Staff Sgt. Mark Olsen)