Air Force aircrew mark a milestone - likely the completion of a combat mission or tour - with a traditional champagne celebration on the flight line. The 'HOBO' lettering on the caps refers to a call sign historically used by USAF Air Commando squadrons flying A-26 Invader aircraft on night interdiction missions over Laos during the Vietnam War, part of a classified program known informally as the Steve Canyon Program. Project: 219143