Not overly interesting photo but the story behind it is. These are B-52s with high altitude contrails heading north over South Vietnam as part of Linebacker 2, sometimes referred to as the Christmas Bombings, a strategic bombing campaign conducted by the USA against targets in North Vietnam from 18 December to 29 December 1972, The operation was the final major military operation carried out by the US during the conflict, and the largest bombing campaign involving heavy bombers since WW2. While flying routine C-130 cargo sorties in South Vietnam, we could hear distressed emergency guard channel calls from B-52 aircrews as they were under attack from SAMs. Number of B-52s shot down were around 15 with several more bing heavily damaged beyond repair. At least a dozen or more fighter aircraft were also lost during the operation.