During world war two, fog was dispersed with a secret weapon called Fido. This stood for either “Fog Investigation and Dispersal Operations” or “Fog, Intensive, Disposal Of.”
Calcium chloride sprays had shown some promise for absorbing fog in the 1930s but, by 1940, the only proven dispersal method was heating on a massive scale. Churchill instructed the Petroleum Warfare department, an organisation originally tasked with creating burning obstacles against invasion, to develop a tool for the job.
Fido was a system of fuel tanks, pipes and rows of burners running the length of a runway. Once lit, it created a fiery scene worthy of Dante’s Inferno, burning a hundred thousand gallons of fuel an hour with a great roaring sound. The flames were visible for 60 miles and the heat could disperse the thickest fog in a matter of minutes. 
The U.S. Department of Defense has been the principal Federal supporter of the research concerning warm and cold-fog dissipation. For the fiscal years 1968 through 1972 the estimated costs for such research will total about $7 million. 
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