The Model 294 (XB-15) was a mammoth experimental bomber that first flew in October 1937. Its cavernous fuel tanks gave the Model 294 the capacity to stay aloft for 24 hours, and the plane's enormous wings astounded those who saw it. The wings were thick enough for a passageway to the engines, permitting the crew to make minor repairs while the bomber was in flight. The U.S. Army used the XB-15 to study the possibilities of very-long-range bombing. However, because it was an experimental airplane, the lone XB-15 did not serve as a bomber during WWII. Instead, the military put the airplane's great loading capacity to good use by converting the XB-15 to a cargo carrier, designated the XC-105.