During the Vietnam War, from 1964–72, the RAAF contributed Caribou STOL transport aircraft as part of the RAAF Transport Flight Vietnam, later redesignated No. 35 Squadron RAAF, UH-1 Iroquois helicopters from No. 9 Squadron RAAF, and English Electric Canberra bombers from No. 2 Squadron RAAF. The Canberras flew 11,963 bombing sorties, and two aircraft were lost. One went missing during a bombing raid. The wreckage of the aircraft was recovered in April 2009, and the remains of Flying Officer Michael Herbert and Pilot Officer Robert Carver were found in late July 2009. The other was shot down by a surface-to-air missile, although both crew were rescued. They dropped 76,389 bombs and were credited with 786 enemy personnel confirmed killed and a further 3,390 estimated killed, 8,637 structures, 15,568 bunkers, 1,267 sampans and 74 bridges destroyed. RAAF transport aircraft also supported anti-communist ground forces. The UH-1 helicopters were used in many roles including medical evacuation and close air support. RAAF casualties in Vietnam included six killed in action, eight non-battle fatalities, 30 wounded in action and 30 injured. A small number of RAAF pilots also served in United States Air Force units, flying F-4 Phantom fighter-bombers or serving as forward air controllers.
Question: How many more bunkers than bridges were destroyed?
Answer: 15494