A B-2 Spirit refuels from a KC-135 Stratotanker during NATO Operation Allied Force. A U.S. Air Force B-2 Spirit stealth bomber refuels from a KC-135 Stratotanker on April 6, 1999, during an air strike mission in support of NATO Operation Allied Force. Operation Allied Force is the air operation against targets in the Federal Republic of Yugoslavia. SHARE: Download: Full Size (0.05 MB) Credit: VIRIN: 908081-L-IXU99-215.jpg Photo Gallery